FEB. 18, 1881. ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 839. boil, lift, wring, and pass into a chrome beck at 6 to 81° Tw., and 77° Fahr. If the shade required is very dark the heat may be raised a little more. Wash well, make up a beck with fustic, extract of indigo, and orchil; add a little alum to draw on the fustic, and acidulate slightly with sulphuric acid for the blue. Dye at a boil, adding more of any of the colours as the shade may reqtire. Another Scarlet. Prepare your silks in stannate of soda at 4° Tw. in the cold; take them through weak vitriol sours, and wash well. Give a second mordant of red liquor at 84 Tw., thickened with calcined starch at the rate of 3oz. per 35 fluid ounces of the mordant. Dry without rinsing for at least twentyfour hours; then rinse and dry with decoction of cochineal. When the colour is as deep as is required add nitrate of tin to the same beck. This process gives scarlets as fine as the former, and The object for with less loss of colouring matter. the addition of calcined starch is to give the silk more body. In many dyeworks scarlets or silks are grounded with annatto. Aniline Blue Dyed with Soap. For 11lb. of silk add to a water 171oz. sulphuric acid, and 3oz. solution of white soap. Stir well up and dye at 158 Fahr., with 1oz. aniline blue, which is added in four successive portions. Wash, brighten with vitriol sours, and rinse. Aniline Violets. Aciduate the water very slightly with sulphuric acid and enter the silks. Begin to dye in the cold, adding the colour in small successive portions. Raise the heat gradually up to a boil to level the shade. If the tone is too blue let the beck cool, and take the silks through again. They are then brightened by one or several successive passages through vitriol sours, and it must be remembered that heat increases the blueness and lessens the redness.-Chemical Review. culations should be so little known. will show you The labour and fatigue of manipulating long series of figures for nautical and astronomical purOne of the earliest attempts by poses had long been felt to be irksome to those engaged in it. mechanical means to lessen and facilitate this labour was made more than 250 years ago, by the land; and as this attempt was the precursor of immortal Baron Napier, of Murchiston, in Scotlogarithms, and the subsequent slide, it is necessary to allude to it. The invention consisted of a was called the "index-rod," and also ten others, number of flat bone or ivory slabs, one of which It may be supposed that at first the sliding-rule was not much used, if only from the difficulties own digit. By placing these rods side by side, so one for each of the digits, headed at top with its that the top figures exhibit the multiplicand, and "Abroad deriving from the index a line of figures, corre- experienced in its construction. This may be sponding to each number of the multiplier, the judged of somewhat from the following extract to find out one to engrave my tables upon my new quotient is obtained by simply adding these figures from the interesting diary of Mr. Pepys. Under together, no knowledge of the multiplication table the date of Aug. 10, 1664, Pepys says: being necessary. Division was effected in a some. what similar manner, but even with these aids sliding-rule with silver plates, it being so small arithmetical calculations were tedious operations. that Brown, who made it, cannot get one to do it. their saving so much labour, for they did not do it, and I set an hour beside him to see him design It was not that the rods were esteemed because of So I got Cocker, the famous writing master, to do so; but it was that from the simplicity of the it all; and strange it is to see him, with his natural operation, more accurate results were likely to be eyes, to cut so small at his first designing it, and obtained, than by the ordinary methods of multi-read it all over, without any missing, when, for plying and dividing. From the circumstance of my life, I could not, with my best skill, read one the rods being made of bone or ivory, they were word or letter of it." To this entry Pepys adds, smallness of work. It cost me 14s. the doing." called "Napier's bones," and they have been more the next day, "Comes Cocker with my rule, which frequently noticed in historical works than in those he hath engraved to admiration for goodness and relating to their use. The prices of those days were high, as compared with those of our own time, when, for a few shillings, a rule may be obtained of greater accuracy, and in a more convenient form than was then charged for merely marking the divisions. 66 As a It would be altogether beyond the purpose of this sketch to enter minutely into the construction of logarithms, but it may be briefly said that they are a series of numbers in arithmetical progression, corresponding to others in geometrical progression, by means of which complex and lengthy calculations can be made with lightning-like rapidity, combined with perfect accuracy and ease. practical illustration, it may be mentioned that the innumerable and tiresome processes for obtaining numbers in a series, which would have to be resorted to were it not for their aid, would almost preclude the possibility of the yearly compilation of such works as the Nautical Almanac, and many kindred works. The radix, or root 1, from which Napier started, being found to be an inconvenient THE LOGARITHMIC SLIDE.* Tthpabilities of Gresham College, in the year 1613, shortly 10 those who have acquired a knowledge of the one, Mr. Henry Briggs, mathematical professor at a matter of surprise and regret that an instrument after Napier's invention, adopted the number 10 conbining such unexampled rapidity, ease, and for the root, as being preferable, and on this basis accuracy in performing all ordinary business cal- logarithms have since been constructed, and upon By its this method huge volumes of nothing but tables of assistance the drudgery of computation is avoided, logarithms of various kinds have been calculated, and the time and trouble expended on mere arith- and remain ready for the use of astronomers and metical workings proved to be a waste of effort; in others, who thus find the drudgery of their labour short, its aid mentally may be safely compared obviated; and an easy, pleasant, and unerring Mr. Briggs, it is rewith the advantages derived from mechanical mode of calculation made ready to their hands. appliances in diminishing the wear and tear of The discovery was looked upon by the learned as regarded it as a miracle.' manual labour. The intellect is freed from the the great one of the age. the great astronomer, distraction of tedious processes, for the statement corded, was "beside himself for joy"; and Kepler, of each question, the operation and the result, are simultaneous and apparent in their connection. Napier's invention was not, like those of Kepler incidences which might have led him to it, but was The laws that govern its operations are few and and Newton, connected with any analogies or coa preliminary we shall be vindicted in simple and easily understood; knowledge of decimals being all that is required, the result of unassisted reason and science; and, and the curiosity of the uninitiated may be stimu says his biographer, lated by learning, that on an instrument as port-placing him in one of the very highest niches in the able as a pocketbook we have the whole gamut of Temple of Fame. Kepler," he goes on to say, his canon for the periodic movements of the numbers; and that whether, as a means for self- had made many unsuccessful attempts to discover unsurpassed instruction or advancement, for utility in business, or for profitable amusement, its planets, and Newton had applied the palpable study is well rewarded in its capabilities for varied tendency of heavy bodies to the earth to the application. Scientific men estimate its value, the system of the universe in general; but Napier man of business appreciates its utility, and it will wrought out his admirable rules by the slow scientruth." be well for the practical mechanic and engineer tific process arising from the gradual evolution of when he learns how to employ it intelligently, instead of carrying it in his pocket, as thousands do, yet unable, through a deplorable ignorance, to avail himself of its extraordinary powers. Small as is the knowledge of it in our own country in which it was invented, it is less known and less used upon the Continent. But it should be recorded to the credit of the "heathen Chinee," that he is not altogether in the dark respecting its merits, the writer being credibly informed that it is frequently seen in the hands of educated Chinese merchants, to the great amazement of many an Englishman, who doubtless regards it as a Pagan device, about as well adapted for its purpose as the slender chopsticks for the conveyance of food to the mouth. In the early part of the seventeenth century Mr. College, invented the sector, and several other very Edmund Gunter, also a professor at Gresham useful instruments, including the surveyor's chain of 100 links for land measuring. He it was who first conceived the idea of marking out, on a scale, spaces whose lengths vary in exact proportion to the logarithmic value of numbers placed over against This scale, so marked, he termed the "line of them. in all respects identical with All the numbers," and it that now in use upon the slide-rule. various operations of multiplication and division of scale by means of a pair of compasses, but these numbers, &c., can be performed on this single were subsequently abolished a few years afterA French writer upon mathematics, half a century ago, wrote that "in England the use of wards by the Rev. William Oughtred, an eminent the slide-rule is taught in all the schools at the mathematician, who first adopted the plan of same time with the letters of the alphabet," placing one scale against another, and sliding statement which, it is needless to say, must be them together as might be required, and hence the taken with more than the usual reservation. One term "slide-rule." He was a man who set little writer has said of it, and justly, that "for a few value upon instrumental aids, unless in the hands shillings most persons might put into their pockets of those who had previously learned the principles many hundred times as much power of calculation on which they were constructed. A pupil of hisas they have in their heads; for the use of the in-William Forster-says that in the year 1630, he strument is attainable without any knowledge of spoke to him of a Gunter's rule he had, six feet upon which he answered that the use the properties of logarithms on which it is con- long, to be used with a pair of "beame com structed." of the compasses was a poor invention, and the "But," said he performance very troublesome." * From an article in the St. James's Magazine. passes SCIENTIFIC SOCIETIES. TH ROYAL ASTRONOMICAL SOCIETY. HE annual meeting was held at the Society's Rooms, Burlington House, on Friday, the 11th inst., J. R. Hind, Esq., F.R.S., president, in the chair. The minutes of the preceding annual general meeting having been read and confirmed, Mr. Rand Capron read the report of the auditors, from which it appeared that the income of the Society during the past year amounted to about £1,450, of which £650 had been expended in printing the Memoirs and Monthly Notices, and £85 in binding and the purchase of books for the library. Captain Noble drew attention to the fact that by the treasurer, but they are also to report as to the the bye-laws of the Society the auditors are bound not merely to investigate the financial statement of The Society possesses some valuable instruments condition of the property belonging to the Society. and other property, which he thought it desirable that the auditors should annually examine. After some discussion, a motion instructing the and other property of the Society, having been put auditors in future to report upon the instruments to the meeting, was carried. Mr. Bidder, Q.C., moved that a motion with renotice had been given by Lord Crawford, Sir spect to the endowment of research, of which Edmund Beckett, and others, should be taken into course were raised by Mr. Christie, Mr. De la Rue, consideration by the meeting before the reading of the annual report. Technical objections to this was agreed that the motion should be taken first. Mr. Dunkin, and others; but on a show of hands it The President having read the notice of the momove-"That a meeting be held in the Society's tion, Sir Edmund Beckett was called upon to Rooms of the Fellows thereof, and such other persons as may desire to attend, to consider the question of the endowment of research by the Government, and that the Astronomer Royal be requested to take the chair at such meeting." Sir Edmund Beckett said: I am not to be regarded as the originator of this movement, although I am one of those who sigued the notice of the motion. I was requested to move that the Society's rooms should be lent for the purpose of discussing whether the endowment of research is desirable or this question. We are not now going to consider not, but we are going to consider whether a meeting should be held in these rooms not confined to Fellows of the Society, but open to scientific men "Endowment of Research." Prima facie that generally to discuss the question. I may, however, say a few words on the meaning of the words was inclined to vote for it seems so good a thing, that I suppose no one here will doubt that it is desirable. When I first heard of the movement, it appeared to me to be so, and to be so feasible that on the subject, and I take it that these words, now without consideration. I found afterwards, however, that there was a great difference of opinion well established by use, mean that though there is at present such a thing as the endowment of work, 560 to personal ends rather than to astronomy. portant that this question should be decided by the for example, of lectureships, of the Royal Obser-interferes with astronomy and directs men's energies vatory, and things of that kind, many of which are doing excellent work, it is proposed to endow something more. It is proposed that certain people should be endowed, and allowed to work at what they like in science. doubt, that people should make researches; but It is desirable, no inasmuch as endowments must come out of the public funds, they ought not to be used to keep men amusing themselves without any result whatever. That is one argument against the endowment of research. But the only point now to be considered is whether you think it desirable in the rooms of this society to discuss the question. I am sure that if there is such a meeting it ought to be presided over by the highest scientific authority, and I propose that the Astronomer-Royal be asked to take the chair. (Applause.) I do not know whether he will accept the duty, but I think that if it is the desire of this meeting that he should do so, he will probably agree to take the chair. This question has now been a moving one for some ten years, and has influenced many people in voting at such elections as are going to take place to-day. Therefore, it is far better that we shonki know definitely what is the opinion of men of science upon the subject. Supposing the meeting should come to the conclusion that it is desirable to have such endowment, there will no longer be any occasion to fight about the question in elections for the council. The matter will be decided and the decision will go to the Government, and will, no doubt, carry a great deal of weight, while, on the other hand, if a contrary decision is come to, there will be little excuse for people continually trying to get gentlemen on to the council because they favour endowment. In other words, there will be no great use in struggling to get the council to adopt an opinion if it is known that the body of the Society has come to a contrary conclusion. (Applausė.) The Earl of Crawford (better known to our readers by his old title, Lord Lindsay) said: I rise to second this motion, and will do so in a very few words. I do not wish to go into the history of past elections for the council, but I will content myself with saying that I do not think that it is desirable that positions should be created where there is payment without corresponding labour. Practically, endowment of research comes to that. I advocate payment by results as much as anyone. In England, above all countries in the world, there will always be plenty of amateurs ready and wing to assist in research, and it is notorious that in England, almost without exception, all the great advances in science have been made by such amateurs; therefore, I do not think that it is at all destrable that the British taxpayer should be required to put his hand in his pocket to provide shares for gentemen who might be working rigatly or wrongly. He could not control them, and while there are such a body of amateurs in the country, I think the researches may very well be left to them. I therefore, have much pleasure in notice of the motion, and I conclude that these that if what Mr. De La Rue says is true with have no such meaning as Captain Noble attributes FEB. 18, 1881. lerian Professor of Pure Mathematics, Cambridge; on the 9th inst., Dr. Lionel Beale, F.R.S. (Presi ROYAL MICROSCOPICAL SOCIETY tion of officers, &c., the report of the Council was that if he is of opinion that the motion is not consistent with the bye-laws, his proper course will be it was not necessary for him to prove the truth of Mr. Bidder said: May I point out to Mr. Christie to move an amendment omitting the part of the the modern theory of aperture in regard to wide. Mr. Crisp said that whilst in the late discussion laws? But supposing that the Society only has opposite view had not been demonstrated as resolution which is not consistent with the bye-angled immersion lenses, but only to show that the power to use its rooms for astronomical discussions, claimed; it would, nevertheless, be useful, be I should like to ask Mr. Christie what he thinks thought, having regard to the gross mistakes into will happen, or who he thinks will interfere with which Mr. Shadbolt and Dr. Edmunds had fallen, us, if we decide to make use of our rooms for dis- to keep prominently before the Fellows (until the cussing this cognate question? Does he imagine fact had been as thoroughly grasped as any propo that the police will be sent in to turn the meeting sition of Euclid) the diagram which illustrated the out? (Laughter.) I think, to be put in this form: "That the council Professor H. J. Smith said: An amendment ought, aperture so great as that of an immersion with be requested to grant the use of the rooms of the diagram now presented was the joint donation of demonstration that no dry objective could have an Society for the purpose of holding a meeting to Mr. Stewart and himself to the Society, and was inconsider the question of Endowment of Re- tended to be hung up in the library until the trafi "balsam angle" exceeding 820. The framed search." This would not in any way pledge the of that demonstration had been overturned. 1 Society to an opinion, which, I think, Sir Edmund was obviously useless for any one to renew the inBeckett's resolution does, and what is worse, it vitations that had formerly been so pressingly give commits the Society to deliberating the question to go and see some measurements of objectives with any persons who may choose to attend the made, or to show how they were fallacions. As meeting and vote upon the subject. I do not pro-well might they respond to an invitation to see s pose to move such an amendment, because I do measurement made of the three squares on the not wish to take part in the discussion on the pre- sides of a right-angled triangle in support of the sent occasion. My reason is, that I have heard view that the two smaller squares were not equal from the speech of Sir Edmund Beckett, and I to the larger one, instead of referring the Mr. Christie said: May I ask under what bye-elections. (Applause.) I think that in the scientific new microscope, of which the construction is based confess that I have heard it with very bitter regret, demonstrator to the 47th proposition of Euclid law this resolution is brought forward? I have world we should be large enough and broad enough on that of Wales's microscope (recently figured in the that this question is made a party question at been looking at the charter and bye-laws, and cannot find any section under which the society think fit on such questions, and should judge of Mr. Crisp exhibited and briefly described Swift's has power to lend its rooms. to allow scientific men to hold such opinions as they ENGLISH MECHANIC). them wholly on their scientific merits. secting the resolution. The Earl of Crawford: I understand that the Society has lent its rooms to the British Medical Asociation to hold a conference during the long Mr. De La Rue sall: With all deference to the moble lord who has seconded the resolution, I do not think there is any precedent for the course that has been adopted. The only case in which the rooms of the society have been lent, was when an application was made to the Council for the purJose. No application has at present been made, and when made, it pught to be made to the Council, who manage the affairs of the Society, and not to the general meeting. of the resolution, I will propose that the words, ford's proposition. I do not wish to speak upon meeting should only consist of Fellows of the by the Rev. J. V. Mummery, that the meeting application of the "Tyrrel" pinions to the moving which, after briefly alluding to the biographies of the presidential address it has been usual at the members of council for the ensuing year:- Mr. Lanyard said: I think it is desirable that the society at large should express its opinion upon the subject, and the Council will then know how The question, as Sir Edmund Beckett has it has beed a ving question for some years. At the meetings of this society it has usually been Ape in the backround, but it has really exerced and is exercising & great deal of influence. The promoters of cowment Lave been very A Boys Commisnom sat for some five Vice-Presidents: Prof. F. M. Balfour, MA Fran takking evidence typon the subject, and pubF.R.S.; W. B. Carpenter, C.B., M.D., LLD. LEGAL NUTZE BATSE time-books, and there has been F.R.S.; J. Millar, L.R.C.P. Edin., F.L.S.; J.W. President, Prof. P. Martin Duncan, M.B., F.B.S at tell of the newspapers in favour tamat Kamar Indeed, more than one EM DL Kilbhed with the intent of read by the secretaries, the president read his ad- M.R.C.S., F.L.S.; F. Crisp, LL.B., B.A., F.LS The report of the Society having been partly M.B., F.R.C.P., F.R.S. Secretaries: C. Stewt Stephenson, F.R.A.S. Treasurer, L. S. No one can doubt that dress (which will be printed in the Monthly Notices) Members of Council: R. Braithwaite, M.D.. importados to science. I am on presenting the gold medal to Prof. Axel Möller, C. J. Fox; W. H. Gilburt; J. Glaisher, FRS. talne that it would have a very for his investigations of the motions of Faye's comet. A. de Souza Guimaraens; W. J. Gray, M.D ett ppl allemse, and upon bodies like was mattuted for the en- Richards and Mr. A. M. Downing having been ap-A. D. Michael; F. H. Ward, MRC.S.; 1. The baile having been taken and Father E. Ingpen; J. Matthews, MD. J. Mayall, jun £ of astronomy, and not pointed scrutineers, the following gentlemen were Charters White, M.R.C.S. Svende, o udang patronage, which only | for the ensuing year: — of getting money out of the declared by them to have been elected as officers Beaks. Before vacating the presidency to his succee Dr. Beale remarked upon the increasing prospe FEB. 18, 1881. ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 830. of the Society, as shown (1) by the large accession of new Fellows, and (2) by the condition of the finances. He could not, he said, claim any credit for this increased prosperity, which was unques tionably due to the zeal and efficiency of the secretaries. He thought a special vote of thanks should be given to the junior secretary for his conduct of the Journal, which not only represented the actual work of the Society, but gave in a more or less condensed form the whole of the current literature of the microscope-from every available English and foreign source. The special vote of thanks to the junior secretary, Mr. Crisp, was carried by acclamation. The new President, Professor Martin Duncan, F.R.S., was then inducted to the chair; after briefly thanking the Society for his election, and expressing the hope that his term of office would be as prosperous as that of the outgoing President, he adjourned the meeting to March 9. TH SCIENTIFIC NEWS. HE first four of a series of recapitulatory lectures upon "The Solar System" will be delivered on the evenings of Tuesday, Feb. 22nd, Wednesday, Feb. 23rd, Thursday, Feb. 24th, and Friday, Feb. 25th, at Gresham College, Basinghall-street, London, E.C., by the Rev. E. Ledger, M.A., F.R.A.S., Gresham Professor of Astronomy. Subject:-Lectures I. and II., "The Sun." Lectures III. and IV., "The Moon." The lectures will be delivered at 6 p.m. They are free to the public. In the middle and at the conclusion of each lecture illustrative diagrams will be exhibited by means of a limelight. The death is announced of Mr. Reuben Orton, who is described as the father of English aëronauts. He had made considerably over 300 balloon ascents, the last being that made under the auspices of the Balloon Society, when he travelled from Chingford to near Cambridge. The Murchison medal of the Geological Society has been awarded to Prof. Geikie. A public presentation was made last week at Truro, to Mr. J. H. Collins, the founder and secretary of the Mineralogical Society, on his leaving the neighbourhood to take a lucrative post in Spain, in connection with mining. Mr. Collins, who has been a frequent contributor to our columns, has long taken a great interest in the Scientific Societies of Cornwall, and we are sure the good wishes of our readers will follow him to his new home. Besides lawyer. For the purposes of its investigations Those who conduct a will-o'-the-wisp to the mariner. revolving lights, there were other distinguishing the Court would have the powers of a Court of characteristics, and one of the most important Summary Jurisdiction. of these was colour; but that was liable to mis- these preliminary inquiries or formal investigaapplication, and at the present moment on the tions are directed to report on the causes of the English coast was leading, and would in the explosion and the circumstances attending it; The paper by Mr. Alex. Adams, of the Telefuture lead to wrecks, unless something was and these reports are to be published by the a series of hair-breadth escapes, and done. It might be said, indeed, that navigation Board. was although he did not wish to frighten people, if graph Department, read at the late meeting of everybody was aware of the actual dangers at the Society of Telegraph Engineers, was folsea, there were some who would not trust them-lowed by a discussion which is still unfinished. selves upon it. In conclusion, he explained his Mr. Adams's observations, made on a wire exown mode of distinction, which was not by tending from Cardiff to London, show that flashes, but by eclipses, and thus the name of earth currents vary in force daily, having four the point would be, as it were, cut out in the maxima and four minima in the twenty-four spell it, but merely to give a simple signal by is that these variations are caused by the moon's motion and position with regard to the earth. A light, although, of course, he did not propose to hours, or rather in the lunar day, for his theory which it would be known. nicely-drawn series of curves and diagrams Another paper by Mr. Aitken on "Dry Fogs' was read at the meeting of the Glasgow Philoso-illustrated this novel hypothesis of the variation phical Society last week, in which the author of the earth currents being due to the position of stated that his further experiments had led to the moon, the coincidence of the one representing the following conclusions:-1, That as regards the varying strength of the earth current with quality and foggy condensation, there was dust another representing the diurnal position of the and dust. Some kinds of dust had the power moon in zenith, nadir, and the ascending and other kinds only the general tone of the discussion, it would of determining condensation in an atmosphere descending nodes being very remarkable. From which was not saturated; form nuclei in super-saturated air; and from seem that no discovery has been made. other experiments it was probable that some In highly degree of supersaturation was necessary before some kinds of dust were active. supersaturated air all kinds of dust would form nuclei and determine cloudy condensation, but in unsaturated air only some kinds were active. 2. That dry fogs might be produced by some form of dust in the air, such as sodic chloride (common salt), thus condensing the aqueous vapour in the air which was not saturated. 3. This condensing power or attraction which some kinds of dust had for aqueous vapour explained even in foggy weather. 4. That as the products why our breath and condensed steam dissolved of combustion of sulphur determined the condensation of water vapour in unsaturated air, and gave rise to a very fine-textured dry fog, they were probably one of the chief causes of our town fogs, as they had a much greater condensing power than the products of the combustion of coal. An improved tricycle with a steam motor, We hear that Dr. E. Hartwig, of Strassburg, has made a more accurate determination of the moon's libration than that of Wichmann. According to the laws which were found by Dominic Cassini to explain the apparent shifting of spots on the moon's disc, and which have been called after him since their publication in 1721, the moon rotates with uniform velocity, the time of rotation is exactly equal to the mean time of the moon's revolution round the earth, the inclination of the plane of the lunar equator to the ecliptic is constant, and the ascending node of the equator always coincides with the descending node of the moon's orbit on the ecliptic. The effect of these laws is the moon's optical libration. But Cassini's laws cannot be strictly true, as they represent only the average state of Dr. Emil Bessels, the chief scientific officer of the moon's rotation; small periodical deviations produce a physical libration, the amount of which is to be determined from proper observa- Hall's ill-fated expedition in the Polaris, is at tions. Hartwig has been using improved instru- present in London. He is to receive the comments, and has deduced his results from forty-mand of an American expedition to proceed up two observations. as soon as seen. The Chemical Section of the Russian PhysicoV.J. Ragosine, of 22, Leadenhall-street, E.C., Chemical Society has offered on behalf of Mr. a prize of 750 roubles for a lamp capable of burning the heavy petroleum oils. The lamps (three specimens) must be sent in before Jan. 12, 1882. Further particulars can be obtained of the Ragosine Company, at the address above given. An examination of railway employés in Brussels has disclosed the fact that 5 per cent. were with the rules, they have been removed from colour-blind, more or less, and, in accordance posts in which the ability to distinguish colours is of importance. different tale. some of It M. That germs of disease may live long, seems to animals that died be proved by recent experiments of a French ground where Committee directed by M. Pasteur. Seven sheep were led daily, for a few hours, to a piece of anthracoid disease, or charbon, had been buried twelve years previously. Two of them caught the disease and died. There was no grass for the sheep to cat, and it is thought those two must have received the germs in the course of smelling about the ground, as sheep generally do. may be added that on some ground of that farm, He knew of none, but where diseased animals had been buried, vegetables are now grown; and M. Pasteur asked the farmer if any employés, &c., about the farm had been affected. same kind of disease) on his own face. showed a healed sore of malignant pustule (the The disease, too, might be comPasteur supposes that if the vegetables eaten had municated by the agency of insects, &c. not been cooked, there might have been a Preparations for the Paris Electrical ExhibiThe general In view of the present difficulties of the Government no attempt will be made to obtain tion are being made with energy, their countenance for another Arctic expedition, Commissioner proposes to have 600 electric lightrequired. This matter has been much discussed, but maps and charts will be prepared and in-centres for the Palace itself, and he calculates and a circular has been addressed to possessors formation gathered up which will be of use to that a force of about 800 horse-power would be future explorers. of systems of electric lighting, and makers of steam-engines, with a view to securing the best have a department of electric toys. The various distribution. No system will have monopoly, as the object is comparison. The exhibition is to telephone systems will, further, be represented, and one interesting project is that of placing in the acoustic centre of the opera a transmitter, circuit, with powerful transmitter and the consending the music to the Palais de l'Industrie. It is also intended to have a very long telephone a force and distinctness hitherto unknown. denser for reception; the latter gives the speech International Exhibitions have often given birth to permanent institutions in the cities where they have been held; witness our Crystal Palace and while not looking for a new edifice as a result of the Palais de Trocadéro in Paris. the electric exhibition, desires that the event might bear fruit in three ways, viz., the formation of a society, a library, and a museum of electricity. Jones's Sound. The United States Senate have passed a In connection with the Naval Exhibition at Glasgow, Sir W. Thomson delivered a lecture on resolution appropriating the sum of £35,000 for "Lighthouse Characteristics" last week, in the purpose of fitting out an expedition to search which he stated that the primary object of a for the Arctic exploring vessel Jeannette and the lighthouse was to be seen and to be recognised missing whalers, which some believe to be imLighthouse officials stated prisoned in the ice near Wrangel Land. Mr. Hugh Mason has introduced a Bill to quite correctly that penetrative power was the The Bill directs first quality for the light, but when there was, Parliament for making better provision for inas frequently happened, doubt as to what that quiries into boiler explosions. light was, it became obvious that lighthouses that on the occurrence of an explosion notice of had achieved but a small part of the task that the various circumstances attending it should be The maximum penalty for was to be achieved. Flashes of light, said Sir sent within 24 hours to the Board of Trade by W. Thomson, were not of much use distinguishing feature, because even supposing not complying with this direction is fixed at £20. the revolutions to be regular, at present they The Board of Trade is thereupon authorised to were, generally speaking, liable to be 5 per cent. appoint an engineer to make a preliminary The times when their guidance was inquiry; then, if it be deemed expedient, to have most needed were those when it was impossible a formal investigation held by a court consisting to consult a chronometer, so that they were like of two practical engineers and one competent wrong. as a the owner or user. L' Electricité, An account appears in Dingler's Journal of device by Herr Fried, applying electric curre " For controlling the action of electric-light f w'.c. • In order to facilitate reference, Correspondents, enhem peaking of any Letter previously inserted, will oblige by mentioning the number of the Letter, as well as the page on which it appears. to the closure and opening of water-valves, whereby e.g., the freezing of water-pipes may be inchines, M. Debrun (we learn from La L LETTERS TO THE EDITOR. avoided. Between the poles of two horizontal Electrique uses a very simple sort of measure of horse-shoe electro-magnet lies an armature, electric energy. It is a very long magnetising | We do not hold ourselves responsible for the opinions of which is attracted by one or the other magnet coil, fixed horizontally, the core, half-iron, our correspondents. The Editor respectfully requests that ail according as the current is sent. The armature¦ half-copper, forming one of the sides of an; communications should be drawn up as brufy as possible.) All communications should be addressed to the EDITOS of the is fixed on a double lever, and through it causes articulated parallelogram. Under the dynamic simultaneously a closure of the main-valve and attraction of the coil, the core enters it more or ENGLISH MECHANIC, 31, Tavistock-street, Covens-garden, an opening of the discharge valve. The lever, less, according to the strength of the current: All Cheques and Post-office Orders to be made Payable to however, does not move the valve piston itself and a counter-weight serves as antagonisti J. PASSMORE EDWARDS. it merely opens and closes a smaller valve, which, force. An index, fixed on the rod, is displaced opens or closes a way of outflow for the water with it, and moves before a scale graduated in above the piston; in the former case, the valve-tenths of webers, indicating, at any instant, to piston is raised by the water-pressure on it from the man in charge, the intensity of the current "I would have everyone write what he knows, and se below in the other the water under pressure furnished. M. Debrun has noticed that a dispasses through the piston itself, the pressure placement of the index 1etm. on the scale suffices much as he knows, but no more; and that not in this only, but in all other subjects: For such a person may above and below the piston becomes the same, to show whether the carbons burn by the point have some particular knowledge and experience of the The coil-wire is 4mm. dia- nature of such a person or such a fountain, that as to and the piston sinks, in the case of the main- or by the base. other things, knows no more than what everybody does, valve by its weight, in the case of the discharge meter, and 2 metres long.) and yet, to keep a clutter with this little pittance of his, valve, by reason of the rubber disc on which the The first part of a valuable work by M. Alph. will undertake to write the whole body of physicks: a vice Milne Edwards, on ** piston rests. The Fauna of Austral Re- from whence great inconveniences derive their original." ions," has been presented to the French-Montaigne's Essays. Academy. The geographical distribution of It is remarkable (and would hardly have been expected, that! birds is chiefly dealt with. these animals are eminently adapted to reveal the existence and position of the zoological centres whence the various species have radiated. The penguins are specially interesting in this respect. They appear to have migrated from a centre of production in the Antarctic islands Lear Victoria Land, and to have followed the great currents going northwards, reaching the waters of Cape Horn, the Falklands, New Georgia, the Cape of Good Hope, and various islands of the Indian Ocean, establishing, in each case, powerful colonies, with 'in time, distinctive The Union of German railways have published certain prescriptions to be satisfied in the steel rails they use. The tests to be made in the works are these; a rail placed on two supports, one metre apart, must bear a load of 20 tons for several hours, without permanent flexure. In like position, it must bear without breaking, two strokes of the monkey of a pile-driver, a weight of 500 kilogs. falling 4 metres; and without any injury, a fall of the monkey 2:50m. The rail must be capable of being bent in the cold state either way to the extent of 50mm., without showing cracks or fissures. It must be capable of bearing a curvature of 22-5 mm. in 3 metres of length. The Russians, it may be remarked, - CHOICE AMERICAN MICROSCOPY Journal, II. (1881), p. 13, I observe a note headed further test how rails bear shock after having characters. Another colony, represented by the not fair to judge of the opinions of American been placed in freezing mixtures. The influence of cold on the resistance of steel is apparent from recent statistics (Deut. Ind. Zeit.) of fractures of steel rails on Russian railways in 1870. Thus in Jan., Feb.. March, and Dec. The numbers are C32, 598, $54, and 692, respectively; while in June they fall to 160, and in August to 156. favoured by Humboldt's current, has gone to brick of gold, measuring 123in. in length, 7in. in breadth, and 4in. in thickness. It was 950, fine, weighed 3785-170z. Troy, and was valued 1-50th. Let me assure the Editor of that journal that I the showmen" alluded to. From the former we do distinguish American "microscopists" from have learnt much, and I do not think I have failed in my acknowledgments. As to the latter individuals, they cater for our amusement in a harmless manner. So long as they do amuse some of us, I suppose we may well drop our "dollars" or even object to the braggart assumption of these showmen that would impose upon us the belief that they are other than showmen." According to M. Raoult, if a small quantity of quicklime (say lcc), in fragments, be put in a glass balloon, the latter heated on a gas furnace to the temperature at which the glass begins to soften, the flame then put out, and a rapid current of dry and pure carbonic acid sent into the balloon, the lime absorbs the gas with remark-serving earthquakes is in course of formation."cents" into their hats. At the same time I able energy, and soon becomes incandescent. The phenomenon is quite visible even in daylight, but is more striking in semi-darkness; with 100gr. of lime, the incandescence may last a quarter of an hour. A French and Germon technical vocabulary has been published by the Brockhaus Library. It is by Dr. Wershoven. In reply to "E J. F. S." (letter 18233, p. 465), that some one should write a paper explaining what should be the average test for objectives of different focus. The test-objects themselves are so very variable that one cannot place reliance that any description of them would answer the purpose suggested, viz., that the intending purchaser should know what to expect for his outlay. In Switzerland, a regular organisation for obBerne, Bale, and Geneva have been designated for principal stations. Prof. Heim has been charged to give a popular expose of the subject, so as to awaken interest and facilitate the institution of as many secondary stations as possible. The country is mapped out into seven districts, and one sarant appointed to collect observations in each; 200 copies of a list of questions are furInished to each. The choice of seismometer for At a recent meeting of the Berlin Electrical the secondary stations has not yet been fixed. Society, subterranea. cables, under various The Trocadéro Observatory, at Paris, has The intending purchaser has two main consideraaspects, were disc. Dr. Brix presented a been opened for some time. Last week M. Leontions before him. (1) Is he anxious to be provided memoir on the measurement of their conductivity. Jaubert gave his first lecture at the Trocadero. with the best objectives that can be obtained without Dr. Ludwig gave a résumé of observations in The lecture was illustrated by an interesting regard to expense? or (2) Has he a limited sum at various countries of the influence of the aurora collection of plans, reflectors, and object-glasses, his disposal and wants the best that can be included of 14 August, 185), on telegraph lines; he also referring to the instruments described on page opticians and ask to be shown the best they supply; in that sum? To the first I say, Go the round of the read a paper on perturbation of underground 228 of the ENGLISH MECHANIC. you will find your choice reduced to that comlines by thunderstorms (such an influence really Some years ago Mr. Pepper created some monly known as "Hobson's," if your experie ce existing, though not strong enough to stop the sensation by undertaking to make sugar from old accords with mine. (I here suppose that you will service. The time and direction of thunder-shirts. Sugar is now manufactured in Germany be strictly guided by what you see, not by mere storms could be indicted from those disturbances. from old rags. The rags are treated by shoptician's" talk. The more candid of the From the discussion it would appear that certain sulphuric acid and converted into dextrine; opticians will at once tell you where first-rate obslight accidents in connection with underground this is treated with a milk of lime, and is then jectives are made) To the second I should say, liues may be due to a sort of return shock, through subjected to a new bath of sulphuric acid which Get the catalogues of the various makers, and go accidents of aerial-lines, propagated by induc- converts it into glucose. The glucose obtained be shown a standard image, and note what is the length of your purse; but in every case ask to by this process is identical with that of commerce, shown, paying little heel to what is said, except to and may be used in the same way for confer- enable you to estimate whether you are dealing tions, ices, &c. When the manufacture has be-with a practical optician or a mere sales. The come more abundant the price will doubtless be salesman is. in my estimation, a very bite noire : very small. It is known that a large number he will shuffle with you, and offer to lend you the of substances are capable of transformation into lenses that you may try them yourself, but he won't glucose. The cellulose of fibrous tissue of wood, show you anything worth seeing with the microtreated with sulphuric acid, is changed into scope. He will be too busy, or will excuse himself dextrine and glucose, and glucose is industrially otherwise. Above all, I would caution everyone most urgently against the second-haul market. produced from starch. As regards microscopical appliances (I mean A singular surgical operation has been per-optical work, not mere brass-work), the secondformed successfully (we learn from frys hand market is .... "rubbish may be shot Rendas, by M. Koeberié. It is the amputation here." of no less than two metres of the smaller intestine! The subject was a young woman of twenty-two. tion. num. A short time ago M. Trouvé described his polyscope, an apparatus for examining cavities of the body with the aid of incandescent platiA recent development of the principles by him is this: A hollow metallic probe has, at a certain part, one or several lateral apertures, and there is also a total reflection prism, the hypothenuse face of which is inclined 45% to the axis of the probe (one of the lateral faces being then at right angles, the other parallel, to the axis, the latter closing the aperture). A platinum wire, to be made incandescent, is placed in the probe, near the prism. The light from it is reflected, and the bundle of rays illuminates all the parts of the cavity opposite the aperture. The light diffused by the parts thus illuminated takes an opposite path, is totally reflected, and comes from the prism, along the probe, to the eye of the observer at the end. Very distinct observations can then be made. ERRATUM.-P. 558, in statistical note on shipping of Hamburg, near middle of note: Last year 6,887 emigrants. For "6.887," read 68,887." (The source of information here is the Deutsche Industrie Zeitung.) The second-hand market is largely used by opticians themselves to get rid of their inferior appli ances, especially their indifferent lenses Therefore, he is offered "So-and-So's "1-5 or 1-12; heshouli the amateur cannot be too much on his guard when take it for granted there has been a glut of such lenses, and that the delightfully bland salesman is simply trying to "catch a fish.' To H. P.," query 12691, p. 505: Monochro 17 219 17 45-4 15 38-9 16 24 13 8.53 9.21 14 15 14.4 15 10 39 11 2 The times of the observed passages are partly, can be reconciled with uniformity of motion. The JUPITER AND SATURN. times of any trustworthy passages, which they may As regards other spots, of which passages across chromatic light is chiefly useful in microphoto- JUPITER-CONJUNCTIONS OF VENUS, to delay the publication or communication of the A Fellow of the Royal Microscopical Society. MICROSCOPICAL. 1830. Aug. 30 [18391.]-I FEEL, with E. D. W." (letter 18346) I do not quite agree with "E. D. W." however, 20 Observed Passages. Gr. M.T. 17 11 4 111 Observer. Rotat. 870-43°. о 18 11.2 Barnard 302-7 316-9 332-5 265.5 277.6 326-5 269.8 310-7 324.6 253-8 267.7 307.2 310 + Williams 310-3 324.2 325.4 338-7 250-2 268-3 281.6 339.4 252.8 266.7 |