FEB. 11, 1881.

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 829.

[We do not hold ourselves responsible for the opinions of
our correspondents. The Editor respectfully requests that all
communications should be drawn up as briefly as possible.]
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ENGLISH MECHANIC, 81, Tavistock-street, Covent-garden,
All Cheques and Post-office Orders to be made Payable to
J. PASSMORE EDWARDS.

W.0.

In order to facilitate reference, Correspondents, when speaking of any Letter previously inserted, will oblige by mentioning the number of the Letter, as well as the page on which it appears.

"I would have everyone write what he knows, and as
much as he knows, but no more; and that not in this
only, but in all other subjects: For such a person may
have some particular knowledge and experience of the
nature of such a person or such a fountain, that as to
other things, knows no more than what everybody does,
and yet, to keep a clutter with this little pittance of his,
will undertake to write the whole body of physicks: a vice
from whence great inconveniences derive their original.”
-Montaigne's Essays.

THE RESEARCH FOR ENDOWMENT-
SPRENGEL PUMP-PLANETARY CON-
JUNCTIONS-XVIIth CENTURY EPHE-
MERIDES THE ROYAL ASTRONO-
MICAL SOCIETY-BALL'S DIVISION
IN SATURN'S RING-WORK ON THE
EYE, &c.-REFLECTING TELESCOPE
-REDHILL CATALOGUE-NEISON'S
LUNAR MICROMETER-TRANSIT OF
MOON'S CENTRE DERIVED FROM
HER LIMB-SATURN'S

OF

THAT
SATELLITES.

I am extremely sorry to be compelled to express
saw a
my inability to answer the query (42703) of Mr.
Brown, in p. 505. The paper in which
the New York Times, and I have hunted high aud
précis of Professor Rood's descriptive essay was
low for it without any result. Hence I can only
imagine that it has been torn up. In its absence
my memory fails me wholly as to the details of Mr.
Rood's improvements; of which I can only now say
that, as far as they were described in the news-
remarkably ingenious. Almost as a matter of
paper, they struck me, at the time, as being
course, though, the American National Academy
of Science, must publish its proceedings, as our own
British Association does. Probably an appeal to
some of our Anglo-American booksellers would
enlighten Mr. Brown on this point. Should he be
unable to obtain a sight of the volume, I will make
inquiry as to whether it is sent to any Scientific
Library in London; and, if so, will not forget to
look the matter up whenever I may next visit the
Metropolis.

I was not, I may tell "W. S. F. (query 42724, p.
505), present at the last meeting of the Royal
Astronomical Society, but can scarcely conceive
that so profound and accurate an astronomer as
Herr Marth can have used the word "conjunction"
in its strictly technical sense, in connection with
the proximate approach of Jupiter, Venus, and
Saturn. The three planets will, about the end of
February, form a striking triangle (in which
Venus will be at the apex) in the sky; but they
certainly will not all have either the same geocentric
longitude or right ascension simultaneously. I don't
think that Herr Marth can have been joking, but
simply that he must have employed a technical
expression in an untechnical way, in inviting atten-
tion to what will really be rather a striking
phenomenon.

notes

intrigue, a mere sucker of other men's brains, predecessor. It is noticeable that the monthly The backbone of the whole agita- lowed at the present day by "Zadkiel." DoubtLETTERS TO THE EDITOR. and an appropriator of the work of his (so-called) arrangement of his Ephemeris is very nearly fol"assistants." tion for endowment is, however, the party of less the parasites of that degraded creature, Brompton pluralists, who each, holding several Charles II., believed all this stuff, with as much, appointments already (of which the general public or as little, justification as people can allege for krows literally nothing), are perfectly ready and their faith in the so-called "Hieroglyphics" which It appears that the Annual Meeting of the Royal content to accept as many more-or rather the survive in certain almanacs to the present day. over without a contest. Certain gentlemen, needsalaries for them-whether they can fulfil their duties or not. The parasites and hangers-on of Astronomical Society is not to be suffered to pass Science, these people advertise themselves and one another without ceasing; and are instant, in season less to be here referred to, who consider their own the public funds, of sinecures for themselves and clerk) freeholds, are clamorous for an infusion of and out of season, for the establishment out of seats on the Council as (like the office of a parishtheir friends. The sole legitimate way in which otherwise-"fresh blood." Yielding to this not ance of science is by payment for results; and their own body, our Council have issued a "House national money can ever be devoted to the further- ostensibly unreasonable demand from members of until some feasible scheme can be devised for List," in which appear the new names of Mr. doing this, I earnestly trust that the Legislature Campbell, Mr. Darwin, and Major Herschel. But sical Observatory" set is notorious, to sit as their will firmly set its face against endowment in any the party who dine at Willis's Rooms want Dr. It does not require an Isaiah to procolleague. form, no matter how loud the mendicant whine Schuster, whose connection with a certain "Phyfor it may wax. servatory question, or any cognate one, cropped up, phesy how he would vote if the Spectroscopic Obso an anonymous circular is sent round, disparaging Mr. Campbell, and asking the Fellows of the Society to expunge his name. If, however, we are going to begin to attack the House List, why, on Mr. Burnham's paper in would ask, should not Sir Edmund Beckett's name appear among those of the Vice-Presidents, and why should the author of the miserably Vol. XL. of the Monthly Notices, retain his seat? foolish He made the Society a complete laughing-stock by this paper, although he scarcely brought it into quite so much discredit and contempt in America and abroad as did the Editor of the precious volume of our Memoirs, bearing the same number. Posa paper by sibly, though, his disappearance from the Council [18358.]-I LEARN, from a copy of one of your table might prove inconvenient to the Tavern suppression or neutralisation. If a man is to appeal contemporaries, with which I have been favoured party, when they wished to "refer by a friend, that a Dr. Heslop (of whose very exsome one not of their own set, with a view to its to his published works to establish his claim to sit istence I was, I grieve to say, previously perfectly ignorant) has been glorifying the Endowment of "Descriptive Astronomy" It certainly reflects Research, before an audience in Birmingham. It on our Council, I wonder who has the greater right would appear, from the address of the gentleman to do so-a mere index compiler, or the author of in question, that the Birmingham Philosophical Society has established a fund for such endowbut little credit indeed on the Society that Mr. ment; which fund, at present, reaches nearly £100 Knobel should sit year after year among its per annum in subscriptions, besides donations to governing body and Mr. G. F. Chambers remain the extent of £900; and that it is intended to out in the cold! I know, from past experience, spend the whole income, however derived, in how the room will be packed by the efforts annual grants to persons living in this town or of the Willis's Rooms party; and how men who neighbourhood, who devote themselves wholly or never otherwise enter our rooms from January to in part to science research." Now to this no obDecember, will be brought up to vote, like sheep, jection can fairly be taken. The donors and subfor Dr. Schuster. I do earnestly hope, though, a small Tavern Club. Until we thoroughly scribers voluntarily part with their money for the that independent Fellows of the Society will purpose (as they believe) of advancing scientific combine to suppress this detestable form of discovery; and always assuming that the form of dictation; this ruling a learned Society by one directed to a legitimate I am indebted to the kindness of a brother- crush the power of this Ring among our repreresearch subsidised object-their action in the matter is commendable rather than otherwise. As long, then, as any man, subscriber to the ENGLIH MECHANIC for two sentatives, we shall never be free from their or any set of men, choose to devote their own quaint and curious old books. The first is the annual attempts to pack a Council wholly and money to the object of endowing research, no more Ephemerides for the seven years, 1652 to 1658 solely with their own friends, and people upon can be said against it than that it is the merest inclusive, computed for the Stationers' Company whose votes they can always count; be the subject matter of history that every great scientific dis- by Vincent Wing; and the second a similar work under discussion what it may. The sooner those covery, without a single exception, has been made for the year 1684, by John Gadbury. Wing was of us whose sole care is for Astronomy, realise ence in his day; and although he disputed the with the Society were it handed over to the clique in the absence of eleemosynary aid; and that where really an astronomer of some pretensions to emin- this, the better. It would be Ichabod, indeed, men are paid beforehand to do a duty, it is notorious that such performance becomes of the most validity of Horrox and Crabtree's determination which now essays to rule it despotically. Do not perfunctory character possible. If, therefore, Dr. of the solar parallax from their observation of the let us deceive ourselves. The South Kensington, Heslop had contented himself with blowing the Transit of Venus in 1639 (himself believing it to or Endowment of Research party, Circular on which I am commenting, trumpet of the society over which he presides, I be equal to a whole minute of arc) he was con- work in every Society, trying, per fas aut nefas, in the Physical Society, should certainly not have deemed his remarks to siderably in advance of his contemporaries in to fill the governing bodies with their creatures. be worthy of any notice here; but as he proceeds many of his ideas. The description of the mode A cognate attempt to that which prompted "Committee on Solar he goes beyond this. After quoting the private of using the tables in the book now lying before the the Brompton assistance which Priestly received, and certain me, and the formulæ and examples which he gives, is being made small grants made by the Fishmongers' Company may even now be studied with advantage. The where again Dr. Schuster's friends are putting him erecting figures of the Physics ") up for the council. These gentry figure and the Pharmaceutical Society respectively, for astrological element is, however, very patent (and a certain member of that paltry little imposof the tions are given for A curious illustration of as the a and w of the list there. Will, or will not, the Fellows of the Royal Astronomical Society specific purposes, he goes on to speak of the throughout the entire work, and elaborate direc- ture, Government grant of £1,000, and £4,000 which the Royal Society administers more Heavens," &c., in it. or less efficiently. And here the cloven hoof peeps the way in which our forefathers utilised the conout. “Our Government," says Dr. Heslop, has, stellation figures is also to be found in the tables submit to a system of "log-rolling" and wire"Root of the private pecuniary benefit of the Brompton Ring? however, as yet made no payment for the labour in the introduction, where we read of "The pulling in their midst, which can only degrade a "Whale's belly," and so on. The strife which has now seemingly become chronic of pure research in experimental physics or Starre in the flexion of Cassiopeia"; "The noble society into an institution worked for the chemistry. A grant from the above sum,' says former horne of the Ram"; Dr. Gore, is often an unprofitable gift to accept, Great Bears tail" because it is in some cases only sufficient to pay The diagrams (or, as the author calls them, in the society was (as is, unhappily, but too well From Chapters on prognosticating the Weather Colonel Strange, and it really seems as though we expenses out of pocket for chemicals and appa-"types" of the eclipses are really interesting. known) initiated by Mr. Lockyer and the late ratus, and allows nothing for skill and labour." Just so, and what business, pray, has Dr. Gore, or from the Celestial Bodies, it would seem that the should never have peace again until we have made any one else, to expect that the British taxpayer Sun-spot quackery is only the development of the a clean sweep of every one of the inheritors of their shall be mulcted even to find him physical appa- astrology of the time of the Commonwealth. most evil legacy. atus, to say nothing of paying him for skill Incidentally, I have learned that, in 1652, the and labour," of which his own estimate would world had been created just 5,601 years; and probably differ indefinitely from anything allied to London built 2,759 years. I have some notion, Griffiths's valuation" of them? And it must be well or ill-founded, that the Stationers' Company Dorne in mind that Dr. Gore is really one of the still publish an almanac with Vincent Wing's nost favourable specimens of those who urge the name on it. As Gadbury boldly proclaimed himecessity for the endowment of scientific research. self an astrologer, of course that element is even It would be absurd to pretend that he is a physicist more obtrusive in bis work than in Wing's. Or chemist of the highest rank; but he is an honest, Some time previously to its publication Jupiter and ainstaking worker in his own field of investiga-Saturn would seem to have been in conjunction in ion, and we may well believe is conscientious in is expressed views as to the duty of the nation in At all events, he is not like more he matter. -han one of the wire-pullers in the endowment

Leo; and three pages and a half are devoted to the
marvellous mundane results of this phenomenon.
Gadbury advertises quack medicines too, a pro-
proceeding which seems to have been beneath his

α

are

at

In connection with letters 18336, 18837, and 18338 (p. 516), I would remark that Mr. Lancaster's really expresses the matter. The shadow of the planet on the rings is

common-sense of the

• I must expressly, and by name, exclude Sir George Although the Astronomer Airy from among this set. Royal is a member of the Club, I know full well that he would strenuously resist any attempt to manipulate the and noble devotion of a long and honoured life to the Royal Astronomical Society for the purpose of providing situations for the "Endowment of Physical Research party or of any of their friends. His own achievements advancement of science, afford the best security that he would decline to connive at anything in the shape of Scientific Quackery.

FEB. 11, 1881.

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 829.

filtering, adding barium carbonate in excess, again
filtering, and evaporating the sweet filtrate till free
from alcohol. The resultant glycerine can either
be concentrated and weighed, or its volume accur-
ately noted, and the quantity of glycerine calculated
from its density in a dilute state.
Alfred H. Allen.
Sheffield, Feb. 5.

press engines of tractive-force of 100 might be ex-
Now, as shown by "C. E. S.," in Vol. XXVI.,
pected to do, theoretically, at least.
pp. 121 and 237, the resistance at 60 miles an hour
on the level = 43-571b. per ton, and the power
exerted by gravity on a body moving down an in-
cline of 1 in 200 being 1-200th of its weight, or
11-2lb. per ton. Adding these together-
43.57

11.2

55.7lb.

being the amount of resistance of a train moving
down 1 in 200 at the rate of 69-8 miles per hour.
which, consequently, is the theoretical limit of
speed in this case.

Now, gravity, acting on a body moving with a
uniform velocity down 1 in 200 generates motion
at the rate of 322ft. per second. In what time

200

=

that the negligence is of that serious character
of manslaughter can be returned, it is necessary
The jury,
known as gross, culpable, or criminal negligence.
It was for the jury to say whether there was gross
neglect on the part of the signalman."
without leaving the box, found Marriott Not
guilty," and he was discharged at two minutes
past six, the trial having therefore, lasted 3 hours
and 22 minutes.

It is to be hoped that the remarks of Mr. Com-
missioner Brown, Q.C., at Chester, and of Mr.
Justice Manisty, at Leeds, will be most carefully
considered by magistrates, public prosecutors,
committed upon a charge of "manslaughter"
coroners, and juries, and that in future there will
be no more cases of railway servants being unjustly
when they have only made a "simple mistake."
Queen's Hotel, Leeds, Feb. 4th.

Clement E. Stretton.

MICROSCOPICAL. [18367.1-REFERRING to letter 18346, I should microscopists to use no objectives of the usual kind, like to inquire the use of "E. D. W." advising but instead to "insist" upon a 4-10th that shali work under a D eyepiece as well as an ordinary to useless for an unknown microscopist to ask for th under the A, when he goes on to say it is "next an objective of the high quality described." He 32.2 × 602 = 289-8ft., or 3.294 miles per hour. says, "my experience is that such work is rarely to be obtained at any cost except by the favoured the use of advising 200 few." Well, then, Sir, what us, ordinary or unknown microscopists, as most of engine us must remain, to insist on an article being supAdding speed maintained by plied to us which in the same breath he tells us it is next to useless to ask for. It looks to me very much like a waste of space.

COLONEL ROSS AND PYROLOGY. [18364.]-I HAVE already expressed my intention not to enter into an argument as to the details of the experiments by which Colonel Ross believes that he has discovered certain facts at variance with the ordinary chemical theories, and his letter on p. 517 shall, therefore, in no way affects my decision. limit my remarks to a reiteration of my belief that the phenomena observed by Colonel Ross are explicable according to the ordinary chemical theories and to an explanation of what I ccnsider to be the of speed per second of 14:37ft. ? second; cause of the opalescence described by him. It is would this force have caused a total acceleration (69.8 miles per hour gives 102:37ft. per quite clear that opalescence is due to a bead con32.2 taining undissolved matter of some kind in suspendeduct 88ft. per second due to engine at C0 miles due either to we get 89 200' sion, and that its disappearance the volatilisation of the suspended matter, to its an hour.) Dividing 14.37ft. by solution in the substance of the bead, or to its abIn the first minute the space covered due to sorption into a ball. When Colonel Ross finds, on seconds as the answer. introducing 5 milligrammes of ignited silica and a ball (of unstated weight) of calcium borate into a bead action of gravity of boric acid, that opalescence is produced, it is explainable in the following way. The silica changes the composition of the ball, a more highly-acidsilicoborate being formed. The production of "opalescent matter" merely indicates a change in the fusibility or solubility of the substances present. Before jumping to a conclusion so entirely unsupported by collateral evidence, and so directly opposed to innumerable established facts, as is the assumption of Colonel Ross, it is only fair that those who support his novel doctrine should take the trouble to quantitatively analyse the ball before and after treatment with silica, and also to examine the bead itself for lime and silica. Also, I would suggest that Colonel Ross should burn 30me amorphous silicon in dry oxygen, so as to obtain a true anhydrous silica, free from the "enormous percentage of some compound of which he supposes ignited quartz to hydrogen contain. If on taking 28 parts of silicon he finds it to combine with 32 of dry oxygen to form 60 of silica, he may be quite sure that he really has got anhydrous silica; and if he finds this capable of producing opalescence, he will be able to convince himself that the phenomenon is not due to water or any compound of hydrogen.

Why Colonel Ross should suppose that quicklime should have a strong affinity for water at a white heat, and in combination with boric acid, I do not know; but it is a well-known fact that slaked lime loses its water at a much lower temperature. If Colonel Ross were correct, one would expect that the lime-cylinders employed for the limelight would be found, after use, to consist of

alaked lime.

66

very nearly Colonel Ross states that he has " What isolated the hydrogen from this hydrogenised boric acid, and got peculiar crystals." meant by very nearly," used in such a connection, it is difficult to say; but if the proof that the crystals are a compound of hydrogen is no stronger than that which appears to have convinced Colonel Ross that ignited silica contains water, he will have much difficulty in convincing the majority of chemists of the reality of his discovery.

Lastly, does Colonel Ross think that any definite proof can be obtained of the presence of water or other compound of hydrogen in the substances exmined, while he conducts the operation in a flame largely composed of vapour of water and other compounds of hydrogen? I am afraid Colonel Ross will find much difficulty in impressing chemists with the validity of his theories while he continues to operate under such apocryphal conditions. Alfred H. Allen. Feb. 5th.

SPEED OF TRAINS. [18365.]-FOR some time past the question of railway velocities has not been mooted in these columns. An opportunity now seems to present itself of asking those who, like "C. E. S." or Mr. D. H. O'Neale Neale, can speak with authority on these matters, to give us information as to how far actual practice bears out theoretical calculations. Given a locomotive weighing, with tender, 65 tons, drawing a train of 150 tons, and able to attain with this load a speed of just 60 miles an hour on the level; assume engine with train passing at the aforesaid speed from the level down a bank of 1 in 200, and the engine worked to overcome the same resistance as when moving on the level, what would be the limit of speed, and the speed during each minute?

The question of weights does not really enter into the calculation; but I mention them simply for the purpose of ascertaining what the new ex

...60

...63.294 Average speed in first mi

nute

After 89 seconds, no further increase of speed can be obtained; and the space covered, due to action of gravity, in S9 seconds =

32.2
200

x 89 637·6ft.
347-8
Deduct space covered in first 60 seconds 289-8
Space covered in next 29 seconds
During last 31 seconds of second mi-
nute the maximum speed per second
1437ft.; and the
due to gravity
14:37 x 31 =
space covered =

.... 445-5
793-3 =
9.013 miles per hour

60

In all subsequent minutes the average speed
Down 1 in 100, under similar conditions, the
would be 69.8.
maximum speed attainable would be 78.45 miles
per hour.

It would thus appear that neither the Midland
7ft. coupled, much less the G.N. Sft. singles, could
exceed a speed of 70 down 1 in 200 with a load of

150 tons.

THE LEEDS ACCIDENT.

V.

[18366.]-YOUR readers will remember that when the three men. Marriott, Brown, and Coe, were brought before the stipendiary magistrate, the two shunters were discharged. Since that time it has jury could find a "true bill"; therefore, I was been understood that, upon the evidence, no grand that "a true bill had been found against all three very much surprised when I received the telegram men," followed by others asking by which train I should arrive at Leeds.

Now, as to letter 18345, and remarks as to close working distance of Hartnack's powers. I am sorry I have no knowledge of Hartnack's specialities, but there are other foreign makers who send out good lenses who allow a little more play for focussing. I have a so-called Gundlach 'th, really about 1-7th, and this has a greater working distance, and quite as good definition as an English in. costing 4 times the price, and I have a Seibert 1-16in. immersion with rather greater working distance. In fact, neither of these ever gives trouble with any ordinary mount, and I have only seen one lens superior to the 1-16th in performance, which was Zeiss' 1-15th, which I thought very slightly better. It is, however, double the price.

Is not the advice to use low powers and high oculars directly contrary to that of every authority on the subject? I think we are cautioned not to trust observations with high eyepieces to anything like the extent we may those made with higher objectives and lower oculars, and when we ought to have some better reason than an increase find the direct opposite urged to general consent we of working distance.

As several questions have been asked lately as to haps my opinion is worth noting amongst others. I think a half-inch, with a power of eyepiece giving what different powers ought to accomplish, per200 diameters, ought to line Angulatum, and such coarse Angulatum as I have seen of Möller's mountA fin. ought to dot a medium Angulatum with A eyepiece without diffiing it ought to dot easily. ciola. The Podura scale differs so enormously, culty, and with a C eyepiece it should dot Fasnot only in size of scale but in coarseness of marking on scales equal in size, that I regard it as a test

TEST-OBJECTS. The trial took place at the Town Hall, Leeds, [18368.1-IN reply to "Fiddle-De-Dee" (No. yesterday (Thursday), before Mr. Justice Manisty. Mr. Firth, M.P., instructed by the Public Prose-42152), with regard to the relative merits of obwood and Mr. Banks for Marriott; Mr. Atkinson curves and sizes not to separate, and achromatic cutor, was counsel for the prosecution; Mr. Lock- jectives made with three sets of lenses of different and Mr. Mellor for Brown and Coe. The prisoners' triplets made to act as three distinct object-glasses, also present. At there seems to me no room for argument in the solicitor, Mr. Warren, was 2.40 p.m. (after waiting half an hour for a jury) matter. Any set of lenses made of the same size the case was opened by Mr. Firth, and at the con- and curves can only be correct for one of the three, clusion of his statement the learned judge expressed and the whole combination can have but a very his opinion" that the case against Brown and Coe small angle owing to so large a part of the light was far too remote," and he directed the jury to from the object being cut off by the back lenses, so of light. This is true even if the greatest care has find a verdict of not guilty against them. This that even supposing the image to be correct it will they at once did, and these two men were dis- not bear magnifying with deep eyepieces for want charged at 3.30 p.m. been taken with the corrections. But the fact is such care never is taken. No maker of repute, either English or foreign, now makes glasses on this principle, and I am informed by a skilled microcorrected even up to their limited angle. copist in the trade that it is impossible to get them

The case against Marriott then proceeded, and
evidence was given as to the facts. Mr. Lockwood
then made a most able address to the jury on
At 5.37 Mr.
behalf of the signalman Marriott.
"do not give
Justice Manisty commenced to sum up, and I very
much regret that the "newspapers
a fuller report of his remarks, because they had
such an important bearing, not only upon this
case, but will be of great use and value in the
future. The important passage to which I refer
was the "law," as explained to the jury. The judge
pointed out that there are very different degrees of
"An error of judgment, a simple
negligence.
mistake, or an accident is not sufficient to sustain
an indictment of manslaughter." Before a verdict

of I wish to impress upon the beginner in microscopy that in choosing good objectives, moderately wide angle, he gets, not three, but at least five objectives in one, as by the use of different eyepieces he can get with effect powers ranging in a lin. from 50 diameters to 280, and in a fin. from 250 to 1,100.

"E. J. F. S." (letter 18293) wishes some experienced microscopist to write a short article on test

PREVENTION OF EXPLOSIONS IN the leaders of these faults, in which are stored up, at COAL MINES.

the size of a large walnut, the gas turned on and lighted. In a short time a good bright fire with a red flame was obtained; the external temperature at starting was 32° Fahr., and that of the room 45° Fahr. This latter rose within two hours to 629 Fahr., and was maintained as long as the fuel lasted-viz., 15 hours, the gas and coke burning

brightly the whole time.

AXIOM OF PARALLELS.

and the duly moulded curve traced with a pencil; neck, and all sawed with a fret-saw from the solid, the transverse bar which I recommended might also be scribed on this board, and, together with the The bar should be raised higher than I have shown to be afterwards thinned, shaped and polished. it in the drawing (page 470), so that it would form a sort of front or belly, having the long slits-the representatives of the f's on either side; it ought to be triangular with the flat side up.

Helmholtz's Lectures, on p. 460, have induced me [18373.]-SOME sentences of your review of lels which seems to me to be rigid. It is not likely to ask you to insert a proof of the axiom of paralthat anything new should be obtained on such well-explored ground, yet I have not met it in print myself. I should be glad to see the opinion of some of your able correspondents as to the flaw, if any, in the reasoning. Making these assertions. 1. Two straight lines cannot inclose a space. 2. Two indefinite straight lines cannot coincide in part unless they coincide altogether. straight lines which make equal corresponding A second set of trials were then made under con- angles with a third will never meet if continually so improve sweetness of tone, could be rinsed with produced (Euclid I., 28), and of course the three postulates and nine universal axioms of Euclid. I first prove

The result of a number of these trials, with an expenditure of 281b. of coke, was an average consumption of 325 cubic feet of gas, the expenditure of the latter being very accurately ascertained by passing the gas through a standard test-meter.

ditions precisely similar to the above, with the exception that the gas was used only for lighting the coke at the commencement, and when a good fire was obtained, and the temperature had risen to 62° Fahr., it was turned off and only used again for a short time to re-invigorate the fire and maintain the temperature. This second series of trials, with an expenditure of 281b. of coke, resulted in an average consumption of 50 cubic feet of gas; the fire, when the gas was turned off, was not so bright or rich as in the first series, and the fuel only lasted 13 hours.

Upon the completion of the coke and gas trials as above, the grate was restored to its original condition for burning coal. The fire was lighted in the usual manner, and within two hours the temperature rose to 62° Fahr., as in the previous trials. the external temperature at starting being 32° Fahr, and that of the room 45° Fahr., and with a consumption of 28lb. of coal, 62° Fahr. was maintained for 14 hours.

The room in which the experiments were made was the same in each case, having a capacity of about 3,000 cubic feet, a due north aspect, and situated about 150 yards from the river, to which it is entirely open.

The above facts having been ascertained after an extended and repeated series of trials, in which the fuel was most carefully weighed and the gas measured, it now becomes a simple matter to reduce the results to £ s. d., and in doing so I have taken the present prices of gas, coke, and coal in this neighbourhood, which are as follows: Coal, 20s. per ton; coke, 12s. per chaldron; and gas, 3s. 3d. per thousand cubic feet; from these we obtain the undermentioned results, viz. :

FIRST TRIALS.-Coke and gas continuously for

15 hours.

2.571 d. 12.675 15.246d.

SECOND TRIALS.-Coke with gas for lighting and use occasionally for assisting the coke, for 13

hours.

281b. of coke at 12s. per chaldron.... 2-571d.
50 cubic feet of gas at 3s. 3d. per 1,000
cubic feet...
1.950

Or, 3477 of a penny per hour.

THIRD TRIALS.-Coal only, for 14 hours. 281b. of coal at 26s. per ton

Or, 2785 of a penny per hour.

3. Two

at a point must either intersect or coincide if pro-
PROPOSITION A.-Two straight lines which meet
duced. If it be possible (Fig. 1) let the two straight

E. B. Fennessy.

THE "DEVON SAFETY" BICYCLE. remarks [18375.]-THEORETICALLY, the of "Orderic Vital" appear to be correct as regards the steering of this bicycle, and the danger of getting the feet too close to the spokes, but I am E pleased to be able to state that, although I formed the same opinion myself when designing the machine, I thought, practically, it may not interfere with its successful working, and the practice certainly does not coincide with the theory, as the steering is most perfect and easy (easy it must be from its being vertical), and the feet do not at all work too close to the wheel. The woodcut has given the lever too great length, which would tend to lead to the conclusions of Orderic Vital"; but this arrangement really gives "nearly double the power" instead of less, as the pedals are just twice the distance from the fulcrum than the crank-pin or resistance is; also the great increase of power results from the " weight" being "vertically" on the treadle for nearly the whole stroke." I think the fact of the pendulum oscillating with the downward stroke has been overlooked by" Orderic Vital" regarding the effect of the length of the stroke, since the stroke as now arranged gives the maximum results, which the slightest alteration in adjustment destroys. I am very pleased to receive any criticisms: indeed, sometimes they are very from theory only, I hope, after the machine has useful; but as it is hardly fair to invite criticism that your correspondent will then be able to form been seen and well tried at the Hanley Exhibition, the favourable opinion that I hope it is entitled to, and which practice has decided to my own satisfaction. One point of safety evidently overlooked by "Orderic Vital" is the great ease of dismounting, as this can be done from the treadle at "any f the rider be considered as a small advantage part " of the stroke, nor must the upright position only.

lines A B C, D B E, not coinciding towards A and
D, meet at B without intersecting. By assumption
(2) no part of DB E can coincide with A B C,
therefore D B E must be altogether on one side of
A C. Let, then, D and E (Fig. 2) denote points on
D B F above A C, and let B' denote the point on
A C which coincides with B. Then if AC be
moved up towards D and E, B' will be above B,
and a space will be included by portions of the two
straight lines; but this is contrary to assumption
(1). Hence the proposition is proved.

PROPOSITION B.-If the two straight lines (Fig. 3)
AD, BE make, with the straight line ABC, the
angle BAD equal to the angle CBE, no straight

SCOPE.

F. Warner Jones.

[18376.]-Procure a box, 22in. long. Sin. Ly Sin. square. At a fix a lens 5in. diameter, 10in. or 12in.

line can be drawn from A between AD and AC so as not to meet BE when both are indefinitely produced. If possible, let AF be a line so drawn. Take the straight lines C'B', B' E', coinciding with CB, BE, and let them be moved towards AD; the HOW TO MAKE A PHOTO-CHROMOangle C'B' E' remaining constantly equal to CBE or CAD. Let B'E' in the figure be that position of L'E' in which it first comes in contact with A F. Then B'E' does not intersect A F, for in that case it must 4-521d. have previously passed through points on AF. And B' E' does not coincide with AF since the angles C'B' E' and C'AF are unequal. Thus, we have two straight lines of infinite length meeting, yet not coinciding nor intersecting, which is impossible by proposition A. Hence proposition B is proved.

3.9d.

It will, I think, be at once seen from the foregoing results that, although by the use of gas and With regard to the assumptions, the first really coke we get rid of the smoke nuisance, that desir- defines a straight line; the proofs of (2) and (3) able end is not obtained entirely without cost, and are found in elementary geometry, and do not that, judging from these experiments, the "coke-involve principle we are seeking to prove. gas fire," while possessing many of the advantages If a definition of intersecting be thought necesclaimed for it, has not proved, in this instance, to be warmer and cheaper than its predecessor, the

focus. bis a slot cut at side (10in. from lens) to amit a carrier or holder, in which to place an uncoloured lautern transparency, opposite and parallel to the lens a. e (lin. behind ) is a sheet of finely-ground glass, resting in grooves, or fastened by pieces of wood glued on to sides of box. dis a drum of an octagon shape (see also Fig. 2), made by cutting two pieces of mahogany (in. thick) to shape stated; fix these on a fin. iron-rod, Gin. apart; the rod should be 9in. long, to allow one end to project through a hole in the side of box, on this projecting piece a knob may be fixed, to turn the drum. Now affix to the wooden ends pieces of various coloured glass or gelatine, and put drum in its place as shown. A mask should be placed in front of the carrier, so that the tints are only seen through the picture. At extreme end of box place another sheet of finely-ground glass, screw on the top of the ox, place a picture in the carrier, and look through the lens; it will be found to be illuminated with beauteous tints. A landscape may appear lighted-up with sunshine in the As a practical method, near enough to the truth, foreground, the valleys enriched with green, a soft "Fiddler " can bend a strip of bright tin plate purple haze on the distant mountains, while an into an approximation of the shape he requires, azure tint o'erspreads the horizon. A slight turn which may be brought to great nicety by focussing of a thumb-screw at side, and the whole scene with it the sunshine on a piece of paper, held at changes as if by magic, moonlight effects are proabout the place of the bridge. Then I would sug-duced, changing again to early morning; the light gest that the strip be laid edgeways on the board creeps on, and ere long a succession of tints of out of which the frame of the violin is to be cut, lovely hue astonish and charm the beholder-no

Possibly, some of your professional readers may find time to pursue the subject further and favour us with the result of their investigations. I have given a good deal of attention for years past to the employment of gaseous fuels, and have made many experiments, but I do not at the present time know of any fire-grate or stove (for ordinary household purposes) wherein gas is employed as the heating agent, either wholly or in part, which gives such THE NEW VIOLIN. good results as the raw material coal. At the [18374.] I REGRET I am unable to give same time, there can be little doubt but that we "Fiddler 29 a rule to find a true parabolic curve shall yet discover the way to effect great economy such as he requires; but I would remind him that in the use of fuel both for domestic and manufac- our great and generous scientist, Mr. Wenham, has, turing purposes, and ultimately to solve the smoke-like many refined thinkers, been an experimenter nuisance question; but whether it will be by separating the raw material into its several constituents, and bringing some of them together again under different conditions and proportions when being consumed in a gas-furnace or grate, or by better and more perfect appliances for effectually burning the fuel in its raw state, has, I think, yet to be settled. The question, however, is one which concerns all alike, being a matter of both personal and national interest.

J. A. C. Hay. Royal Arsenal, Woolwich, January 29.

with the violin, and can tell us a good deal about
the theory of acoustics, on which its perfection de-
pends. I hope his attention may be attracted
towards this unique, simple, and curious fiddle.