"divided by several lines concentric with the circumference, which would lead to the belief that there were several rings in the same plane." After this Quetelet, in Paris. saw the outer ring divided, during the year 1812, with a 10in. achromatic. Captain Kater's observations, which will be found on pp. 177 and 178 of Vol. I. of the R.A.S. Monthly Notices, were made in the years 1825 and 1826, but were never published until 1830. He, like Short, saw several divisions in ring A. Proctor, in his exhaustive book on "Saturn and its System" (which "Ara " ought certainly to obtain), seems to opine that these markings are not by any means all permanent. I have myself seen the division in Saturn's outer ring with a 4 Dallmeyer achromatic; it requires, however, a very favourable position of the planet, a superb night, a telescope of the highest excellence, and a trained eye, even to glimpse it. I have looked for it hundreds of times in vain, and only caught it at very, very rare intervals of the most propitious conditions. I must absolutely deny that I have ever spoken in a tone of personal contempt" of Professor Piazzi Smyth, either in these columns (as asserted by Mr. Muschamp Perry in letter 18106, p. 277), or anywhere else: while as for the "bitter personal bias" attributed to me, I can only assert most positively that it has no existence whatever, save in Mr. Perry's own brain. In point of fact it might puzzle anyone (always excepting the vicar of St. Paul's, Alnwick) to imagine how I could have any personal bias, "bitter" or otherwise, against a man whom I never saw in my life. If Mr. Perry will read letter 18090 (p. 256) over again, he will find that I was most careful to separate the Scottish Astronomer Royal from the Ring who are trading on Sunspottery. He has, however, published certain statements in the Astronomical Register, and by such publication invited public criticism. That his utterances in the number of that serial for the month of November are a tissue of pure nonsense, I questiorextremely if a single disinterested reader of them can be found to deny. It is quite irrelevant to talk about his being an "English gentleman" in connection with this, if his English gentility has failed to prevent him from making such a remarkable intellectual exhibition of himself. I wonder, while I doubt, whether Mr. Perry has read the article itself on which I commented. I have myself before now expressed in letters to the ENGLISH MECHANIC my appreciation of some good work (spectroscopic and other) done by Professor Smyth; bat why I should not comment with equal frankness upon such vagaries as this last one, I quite fail to see, even in the light of the protest contained in Mr. Perry's letter. I hold it to be utterly unworthy of any scientific man to be a mere respector of persons, and must decline to accept the tacit insinuation contained in letter 18106, that the position of the Astronomer Royal for Scotland should protect him from criticism which might be legitimately applied to Messrs. Smith, Brown, Jones, or Robinson. Professor Piazzi Smyth may possibly be a personal friend of Mr. Perry's, and the latter may hence feel it incumbent on him to stand up for him. For myself, I decline to recognise the legitimacy of any such feeling in the conduct of a purely scientific discussion, and am content to say with Cicero, "Amicus Plato, amicus Socrates, sed magis amica veritas." I have to thank both "G. L." (letter 18109) and "W. H. C. S." (letter 18110) for the information they have kindly given me relative to the meteor time. I think that" Argus" (query 42126, p. 288), "C. S. H." (query 42134, p. 288) need only It would be only a waste of money for Mr. Coleman (query 42188, p. 289) to buy, or even make, an astronomical eyepiece for such a telescope as the one he describes. In reply to the query (42192) put by "X." on p. 289, I may tell him that the Sun entered the vernal equinox this year at 5h. 13m. 43s. a.m. on March 20th; the summer solstice on June 21st, at 1h. 31m. 20s. a.m.; the autumnal equinox at 4h. 6m. 59s. p.m. on September 22nd; and will enter the winter solstice at 10h. 17m. 58s. a.m., on December 21st. "A. J. K." (query 42202, p. 289) will perhaps be satisfied to learn that the Apparent Declination" of the Sun, as given in the Nautical and other almanacs, may be taken to represent its true declination, for any purpose to which he is likely to apply it; but that in observing meridian altitudes an additive correction for parallax, to be found in the tables, is necessary. He can not "find the sun's true meridian altitude within a few seconds by taking several altitudes immediately before and after apparent noon, using a box sextant reading minutes." He might as well try to measure a line to hundredths of an inch by the reiterated application of a yard measure divided only to eighths. By extraordinary good luck he might once in a way get an altitude to 30", but he must be content as a rule to read (with any confidence) to 1'. As for the correction of these circum-meridian altitudes, writing away as hard as ever I can on the day of publication to catch the post, I have no time to compute an example for my querist, so must be content to copy one bodily out of Loomis's "Practical Astronomy." I presume that I need scarcely preface this by reminding "A. J. K." that his observations of the altitude of the sun's limb must be corrected (1) for refraction; (2) for parallax; and (3) by the addition of the sun's angular semidiameter if his south limb be observed; or by its subtraction, if the altitude of his upper limb has been taken. This premised, I will extract my example from Loomis. "At a station in Lat. 51° 32′ N. nearly, the correct central altitudes of the Sun on the 11th of March were determined by observation as follows: which, being divided by 11, will give 58.96"; 2 cos. Z Sin. " With reference to the succeeding query (42203) on the same page, I think that "A. J. K." will find a description of the use of Chambers's Table of Equation of Equal Altitudes in the "Treatise on Navigation " which they publish. The formula required by J. G. V." (query 42210, p. 289) is that given on p. 181 of Proctor's "Geometry of Cycloids." Assuming circular orbits and uniform motion: let us suppose that the sun's diameter S (= 32′ 36'4" when the earth is in perihelion) is traversed by a planet in time t (by hypothesis 7 hours). Further, let t' be the time in which the sun in his annual course moves through a distance equal to his own diameter: and let us call the planet's distance from the sun x, that of the earth being unity: then On January 1, when the earth is in perihelion, t may be taken as about 12 79 hours. A Fellow of the Royal Astronomical Society. THE ASTRONOMER ROYAL OF SCOT- G. McKoll. [Several other letters have reached us for which we have not space, critising "F.R.A S.'s" letterand some from rather strange points of view. One gentleman, to whom our readers have been at various times indebted for information, seems to think "F.R.A.S." went out of his way to insult the Irish Land League, quite misconceiving, it seems to us, the spirit of the illustration "F.R.A.S." used. theories must be judged on their own merits, and letter elsewhere seems to us a fair reply. Scientific without reference to the position or character of those who propound or advocate them; and denunciation of absurdities must not be confounded with personal ill will to their authors. Mr. McKoll seems somewhat to miss the point. The "Endowment of Research" is a question about which there may be two opinions; but the " endowment of research" into what is not science seems to us hardly likely to benefit many 66 dents." Every penny foolishly spent is taken from starving but uncomplaining stuthe very sleuder educational resources of the nation.-ED.] which we saw on the evening of November 2. I The Sun's meridian declination was 3° 30′ 38" S.. To the charge brought by Mr. Perry, "F.R.A.S.'s" have no doubt that it was identical with the bolide and it was decreasing at the rate of 0.98" in a which (as I learn from your "Scientific News," on minute. What was the true Latitude? Entering p. 276), was seen at Amiens practically at the same Table X. ("Reduction to the Meridian"), with As I have no means of access to the current the hour-angles given above, we obtain the Greenwich observations, I cannot categorically values set down in the last column, the sum of answer the concluding portion of reply (really query) 42045, on p. 286. Taking, however, one single element, the lunar longitude, I may tell Observer," on the authority of Mr. Lynn, that in 1879, from January to March, the mean error in longitude, as determined from a comparison of the altazimuth observations with Hansen's tables, was +8.25"; from April to June, +8.69"; from July to September, +9:48'; and from October to December, +9.48". The mean result for 1879, then, was 904". The mean error for the three preceding years was, 1876, +9.31"; 1877, +8.25"; and 1878, +7 48". In the paper from which I am quoting (which will be found in Vol. XL. of the R.A.S. Monthly Notices), Mr. Lynn says, "I may remark that had the rate of increase to which I Concluded Meridian altitude.. 34 57 17-0 called attention in my first paper on the subject Zenith distance continued, the mean error in longitude in 1879 Sun's declination. would have been about 12", differing from the actual mean error by a larger quanity than cau well be accounted for by personality in observing." "Observer" may consult the last few volumes of the Monthly Notices, with advantage if he can obtain access to them, as he will find several papers of high interest on lunar irregularities scattered through them. Hence we have the following results: ... +1.8 55 2 43.0 -3 30 38 0 Latitude.... 51 32 5 N." The formula referred to is this:-Call the Sun's hour-angle in arc P, Z his meridian zenith distance, his declination, the latitude, and r the quantity (in seconds of arc) he must rise before reaching the meridian. Then TELESCOPIC MATTERS. MICROME- crometers, by which, I presume, "Orderic Vital" engraving, and a succinct account of the firstnamed instrument. number of amateur observers. I may just name, years ago, and that upon his attention being directed as a minor contingency which had its influence, to Mr. Wenham's original paper by the report in If "Orderic Vital" contemplates making his that I found my frequent monopoly of the oven the ENGLISH MECHANIC he at once communicated own micrometer, he has a task before him com- was viewed with high disfavour by the potentates the fact to the journal in which his own description pared to which the making of an achromatic o.g. of the kitchen, and the half-heard observations of was first published ("Zeitschrift für Mikroskopie," is very plain sailing indeed! There is an article "Here's master messing with that sand again "Berlin). Your Reporter. on the Micrometer by "F.R.A.S.," in Vol. made me perhaps feel the shortcomings of my XIX., page 53 " Ours," with an engraving, differ-pretty sand clock in an exaggerated degree, and I ing slightly from that in Simm's work in the ar- dare say had its effect in bringing about the disuse rangement of the "position" circles; it also of an instrument which required so much "cookshows, in addition, the "slipping piece," which is ing," and which gave so poor a return for the usually fitted to the best instruments. trouble bestowed upon it. John Anthony, M.D. There is also a description of a new micrometer THE SAND-CLOCK. [18131.]-WE ought to feel obliged to Dr. Anthony for giving us his experience of the sandclock, and, if others would also give theirs of the various contrivances that are to be found in our columns, it would be of great advantage to all. At the same time, I fancy he has been unfortunate in the quality of the sand he used, as Dr. H. Draper, in his work on the 15in. silver on glass reflector, gives a very different account of one he used in driving that instrument, and with which he took many good photographs of the moon-and it must have been very steady in its action to allow of that. He is also, I think, too sweeping in his condemnation of all cheap drivers for the telescope, and I will venture to assert that he has not fairly tried the cheapest and most simple-that is, the bladder. It is now twenty years since I invented that, and I sent a description of it to the Ast. Register in 1864, and it was copied into our pages in March, 1866, although "Gimes," in letter 18011, states it to be a French invention, though I question if it is not rather a copy. I have a few times since that brought it before our readers, but I have never learned that it has been tried by any. It is all the reward an inventor requires-who gives his invention to all-to learn that he has been useful to his fellows; and I should feel thankful if those (if any) who have tried this plan would give their experience of it. For myself, I can truly say that I have used it from the first with pleasure and comfort, and have adapted it to both refractors and reflectors, and, except from the rats and mice eating the bladder, have never had any trouble with it. I have now obtained an indiarubber football bladder, and believe I am safe from that. [18134.]-THERE are such a large number of astronomers who are using the excellent mirrors of Mr. With and Mr. Calver that the subject brought forward by Mr. Common at the last meeting of the R. A. S. must be a very interesting one to all of them. It was the deposition of dew or moisture on the silvered-glass flat; and various means of preventing it by protecting or warming the flat were suggested. It was stated that this dew proceeded from the observer's body; so it seems we thus get another "personal equation" introduced into our observations in the way of a personal exhalation. I have used, during the last twenty years, telescopes of all apertures, reflectors of metal and glass, and refractors up to 15in. I have been much troubled by the deposit of dew on the o.g.'s of refractors, in spite of dew-caps. The observer's body certainly cannot be responsible for this. I Early in last Spring I got Messrs. Foster (who have found when the first deposit is carefully wiped advertise in our columns) to make me a long bel-off, the o.g. remains clear for a long time. lows; it is 8in. square, and has a rise of 30in. With this, and a weight of 281b. on the piston of the box which contains it, and which box is 11in. square, and has the top and bottom of the bellows fixed to the centre of bottom of box and piston, so that the sides of the bellows do not touch the box to cause wear. With this bellows I drive the azimuth motion of my 15in. reflector, and, although a large and ponderous instrument, the motion is as smooth and equable as I can desire; and when the object is near the meridian, the altitude screw need scarce be touched for a long time. I have also found a deposit of dew on the glass prism of the Newtonian; but I have not been troubled when I have used the silvered flat. But it seems that others have not been free from this trouble; I should much like to hear this subject discussed by some of your able and experienced correspondents. Will you kindly insert this letter for the purpose of calling forth various opinions as to how this difficulty may be overcome? Possibly the fact that my observatory, including If the observer's body be guilty, it entirely settles HOMOGENEOUS IMMERSION OBJECT GLASSES. [18136.]-IN your last number you reproduce from the Journal of the Royal Microscopical Society, a short note and illustration, by an anonymous correspondent, in which he professes to clear up the apparent mystery of an aperture of 180° (so termed) in air. The author of this note assumes a number of imaginary spaces, or divisions, in the circle, spread out like a fan," which spaces in more highly refractive media are said to increase in width till they extend beyond the hemisphere, as shown in the illustration given in the Journal. It seems to me that the author himself cannot have a clear idea of the subject of his note, which, so far from explaining the principle in a practical sense, only makes it more confusing and incomprehensible. The plain fact is illustrated by the following cut: A is the hemispherical front lens of an object A B glass, in close contact with a cover-glass B. The outer angle, or pencil of rays No. 1 of 120°, will pass direct to the focus on the under surface of the cover, if a film of material of the same refractive index as the glass be interposed. Let now a medium of water, having less refractive power, be substituted; total reflection will then take place between the denser and rarer medium, and the rays between 1 and 2 will be reflected up again at equal angles into the body of the lens, reducing No. 2 to an angle of near 971. Instead of water, let there be a film of air between the surfaces; a further angle of rays will then be reflected back up to the inner angle No. 3 of 81° 58', or, say, 820, which is the limit of the angle for a "dry' object-glass. At emergence from the front of the lens, the extreme rays of No. 3 will be parallel with the surface, or 180°; angles No. 1 and 2 are termed "plus 180°," as they must be reflected from the dry surface back into the lens. I assume the extreme angle No. 1 as 120, without asserting that such an aperture has been reached, as I maintain that most of the methods that we have in general use do not measure angles of apertures accurately. There is another statement put forth, that a homogeneous immersion-lens acts in collecting additional "diffraction spectra" from an object. This is nonsense. Where are these "diffraction spectra" supposed to begin-in a telescope image, in a 3in. micro objective, a in. or in. do., or do they crop up in something higher still? All these lenses act on one optical principle, in collecting a "spectra" are simply visionary. I will venture to say that if Dr. Anthony will invest a few shillings in a bladder and tubing, and connect it to the polar axis of his equatorial, as described on page 283 of the 30th volume, he will have no occasion to complain of a cheap driving clock, and I shall feel obliged if he will give our PROF E. ABBE'S STEREOSCOPIC EYE- cone of rays from a point, and these mysterious readers an account of its performance. Nov. 23. Philip Vallance. [18132.]-To answer an inquiry about the kind and quality of the sand employed. That from the sea-shore was carefully avoided, as containing deliquescent salts, and choice was made of the finest drift-sand, called "silver sand" by gardeners, who use it for striking "cuttings." This was carefully washed, dried, sifted, and great care was taken to free it from all kinds of extraneous matter, the exposure to a high temperature being one of the precautions taken. There was no mistake about the source of the damp which caused the sand to clog, and so to flow intermittently. In quasi out-of-doors observations both the metal of clock and telescope would often be streaming with wet condensed from the atmosphere, and as the weight would soon run down, and the sand in the receiver would require to be poured back into the cylinder at short intervals, the main cause of the sand becoming gradually damp was pretty obvious. Perchance matters would have gone much better if the clock in question had been placed in a snug observatory, or even well under cover; but this could not be, and I only give my experiences under circumstances which I dare say are common to a large Nov. 27. PIECE AT THE ROYAL MICRO- [18135.]-I REGRET to find that, by inadvertence, Mr. Lettsom did not say the angles of the prisms transmitting the direct image (38.5°) were intended to secure the precise division of the rays into two equal portions [which is not possible], but to obtain a convergence of the two axes to the amount of 13° 12 × (45° - 38.5°) 13°], which was considered to be the most convenient inclination; while, at the same time, the method of reflection employed insures a larger amount of rays than would be got by reflection from a plate of glass. = Mr. Lettsom also explained that the compensation for the extra distance travelled by the reflected rays was obtained by the application of a different kind of eyepiece to the slanting tube. In the direct tube the Huyghenian eyepiece is employed, in the other a Ramsden form of particular construction. Prof. Abbe has kindly communicated to me the fact that he was unaware that the method here had recourse to of dividing the rays for binocular vision had been adopted by Mr. Wenham fourteen It will be seen by the above that the trains which leave New York at 7.55 a.m., 3.25 and 3.55 p.m., are the fastest on the road, and all make the distance (84-2) between Jersey City and Philadelphia (Germantown Junction) in the same time, viz., 103 minutes. This gives an average speed of slightly over 49 miles per hour (including one stop in the case of two of the trains). This company now runs 33 schedule trains between Philadelphia and New York. Now take the trains on the Bound Brook Line, operated by the Philadelphia and Reading Railroad. The morning train, leaving Philadelphia at 7.30, is their fastest, and I give its schedule time below: Diam. of tubes outside ft. in. tenders given in the list, they will find not only the Sanders hose-pipe, but also the holes through which the Smith's vacuum brake pipe used to Clement E. Stretton. pass. Saxe Coburg-street, Leicester. FAST TRAINS [18140.]-YOUR correspondent "Lively" refers to the "fuss made about the Lord Mayor's train to Scarboro'," and if I properly understand his remarks, states his opinton that the 10 a.m. from Leeds does "every day in fine weather," quite as good running, if not better. The evidence he gives for his belief is, that frequently travelling by this Leeds train, he has The boiler has no dome; a Ramsbottom safety-run successive miles between Grantham and Petervalve pressed to 1401b. per square inch is placed upon it, over the centre of the driving axle. The total wheel base is HEATING SURFACE. ft. in. 0 18 0 26 2 44 ft. in. 68 6 9 This train makes the distance between Philadelphia and Jersey City (851 miles) in 102 minutes (including two stops), which gives an average speed of a little over 50 miles per hour. The run from Trenton Junction to Bound Brook (27·1 miles) is made in 30 minutes, or at the rate of 54.2 miles per hour. The train consists of four cars (including Pullman Parlour car) and one of the Reading new four-coupled engines having Wootten's patent firebox with tender. The trains of this company, as well as those of the Pennsylvania, are equipped with the Westinghouse Automatic brake. Several other trains on this road make the distance between New York and Philadelphia (9th and Green) in 24 hours or less, according to the number of stops. Thanks to "F. R. M. S." for his full answer to my query in regard to measuring the thickness of cover glass, etc., optically. I had already worked out the problem when I read his answer, and had obtained the following formula: D ·Cos. a x d x n, in which D is the real depth beneath the surface; 4, the apparent depth, the index of refraction of the cover-glass; a, the angle of incidence of the illuminating beam; el, its angle of refraction. But for low angles of the illuminating pencil all this is unnecessary; for balsam or glass we may (roughly) take the index of refraction as 15, and work out any case by the simple "rule of three," thus: as 2 3:: observed depth (or difference of depth): required depth. Philadelphia, Nov. 15. .... Total .... ........ 16 sq. ft. tons cwt. 14 0 12 18 Tender in working order THE BRAKE. The driving, trailing, and all the tender wheels are fitted with the Westinghouse automatic brake, one cast-iron block being applied to each wheel. THE TENDER. The tender runs upon six wheels, has an outside The distance from Glasgow to Carlisle is 115 When the gradients are taken into consideration Clement E. Stretton. THE REMOVAL OF SMITH'S VACUUM boro' in 50sec. each. Now, there is nothing very remarkable or praiseworthy in the mere fact of running downhill (1 in 200 for 11 miles between Grantham and Peterboro') at this high speed. It is done, also daily, by a dozen or more Midland expresses, as for example, between Luton and Bedford, and by the G.W.R. "Dutchman" between Blackball Tunnel and Wellington. Also four other G.N. trains run between Grantham and Peterboro' in the same time (34 minutes) as the 10 a.m. from Leeds, viz., those reaching King's-cross at 11.0, 5.0, 5.20, and 9.30, not to mention the "Scotchman." In all these cases, the speed attained might be 80 miles an hour, if thought advisable. What is to be admired is the maintenance of a high uniform speed over a long distance. The Scarboro' thus ran 82 miles from Grantham to York in 86 minutes, including the three slackenings to 10 miles an hour at Retford, Doncaster, and Selby. A nearly uniform speed of 60 miles an hour was kept up for 86 miles-quite a novelty for a narrow-gauge performance. If the 10 a.m. from Leeds does this, or more than this, it certainly is a marvellous train; but "Lively" should remember that the greater the number of miles he asserts to have been run each in 50 seconds, the greater number he thereby leaves to have been run at a rather moderate pace, since the train is timed (and he says "running to time") between Grantham and Peterboro' at an average of 51 miles per hour. It is strange, too, that "Lively " does not entertain a correspondingly high opinion of those other G.N. trains which run between King's-cross and Grantham in 2h. 3min., or less, i.e., at an average for the 105 successive miles of 51 2-5 miles an hour with gradients as steep to ascend as the fall between Stoke Box and Peterboro'. Surely these could "stand in the face of" the train he anchors by, which none the less is, as everyone knows, a splendid express. "If "Lively" judges by the maximum speed attained on one part of the line," he should travel by any one of the new Midland Leeds expresses, and he will experience plenty of what he admires. For my part, I am most struck by long perseverance in nearly uniform high speed, when I can get it. E. Foxwell. 21st November. [18142.1-MR. WEBB is at present trying a new of lighting up the water-gauge on locomotives [18139.]-UPON page 139, I stated that Smith's at night. It consists simply in fixing a reflector to vacuum brake had been taken off all the 36 Mid- the slot which holds the shed-number on those land express engines to which it had been applied. engines which have cabs. This reflects the light This is a fact, but in spite of that I have been from the fire-box on to any part of the waterrequested to furnish the numbers of the engines. gauge, doing away with the lamp which is usually I therefore give the following list. Numbers of 36 express engines which have had W. engines, it will, of course, save no small amount in vogue. Should this be used on all the L. and N. Smith's vacuum brake removed, and are now in oil expenses. The only engine I know of at fitted with a steam brake upon the engine and present fitted with this is No. 733, Chimera," tender wheels, and also with the Sander's auto-stationed at Shrewsbury. Diomed. matic vacuum apparatus. It is quite useless for any person to continue to The are two stars in R.A. Oh. 38m. 43s., and declinacontradict this statement, as many of your readersion 2° 32'; where the planet was, it must have have opportunities of seeing the engines in ques-been one of them. tion, and if they look at the back of any of these Ringham Hall, Norfolk. Charles North. The sketch 8.15 shows the position of the red spot, the white spot, and the shadow of the satellite advancing on the red spot looking like a drop of ink. The white spot so-called (if this is the object, for I have so little time for careful observation, that though I often see the planet I have made no notes) was plainly seen as the sketch-not as a spot, but a white band suddenly and strongly breaking up the sharp dark, upper portion of the euatorial band. At 9.24, the sketch again shows the position of these three interesting objects, I ought to say that the white spot should be a little in advance of the middle of the red spot at the time. As is mostly the case, the definition on frosty nights is, with large apertures especially, most tantalising from unsteadiness, the short intervals of steadiness show such endless detail, that one is pained that a similar motion from E. to W. the past week, that though the skies here looked The Pleiades are now in good position; and it Last evening (27th), at 4h. 45m., I found the seen, not only in the ansæ but across the body of the very sharp and black. The crape ring was well planet. The large belt and one or two finer ones were noticed. Their curvature corresponded with that of the ring system. The shadow of the ball on the ring was slightly concave. No difference of then high. Hilger's half-prism spectroscope was used on Jupiter and the Moon. In the case of tint was noticed in the poles, but the moon was Jupiter the red end of the spectrum was found two or three in the green. The Moon spectrum intense in its tints, but no lines were seen except was very beautiful, the whole system of solar lines, including the bright ones attributed by Draper to oxygen, being sharply defined in great contrast to the solar spectrum of the same day at noon, in which the finer Fraunhofer lines were invisible. with its sharpness and absence of glare, might he The idea suggested itself that such a spectrum, made use with advantage for comparison with the DARK SPOTS ON JUPITER-NEAR [18148.]-THE first dark spot, situate on the belt north of the north equatorial belt, was observed on the centre on November 27, at 7h. 31m., its longitude being 36 28°. It will now be observed to overtake the red spot, and as it is very large and plain, it ought to be visible in a 24in. telescope. Preceding this spot a group of three much fainter ones was observed on November 17th, but on November 27 the last two of these were hardly visible. The lateral division of the north equatorial belt, mentioned by Mr. Calver, letter 18096, and Mr. Goodacre, letter 18105, has been visible, more or less plainly, ever since August 31st. The near approach of Jupiter to a fixed star, mentioned by Mr. Perry, letter 18106, was also remarked. This star may possibly be variable, for on November 19th, at 9h. Om., it was estimated at 9m., while at 9h. 30m. it was rated at 7:5. At 9h. 30m. on November 20 it was 7.5m., and on November 21, at 7h. 50m., it was estimated at 7:0 magnitude, by comparison with the satellites, and of a slightly reddish colour. Its place seems to be R.A. 0h. 38m. 49s., north declination 2° 33' 8". "B. M.'s" inability to see the comes to d Cygni induced me to examine this object with my 5 in. Calver reflector. With powers of 186, 275, 380, and 450 the small star was easy to see, especially with 450. I estimated its magnitude at 7:5; colour, plainly bluish. With all these powers the disc of the large star was beautifully clear and distinct, and surrounded by one moderately-bright ring; no rays or flares of any kind. This was on November 17, at 7h. 30m.; the moon was nearly full, but low down; definition nearly perfect. Brighton, Nov. 29. A. S. Williams. HELPS FOR RAMBLING FISHERMEN. [18149.]-THE accompanying sketches represent useful devices for a rambling fisherman :-A is a ning to bestir themselves, and I do not think that I 20 10 180 170 160 150 30 40 50 60. 70 66 say which he sees most distinctly, for he will bring O 140 130 160 -170 -10 20 30 40 50 60 180 page so that the accompanying diagram of rings people are astigmatic, but some very little; and I can be slid along the rule while it is held at am inclined to think that if the longer focus is not right angles to its upper surface. We will test the more than half to three-quarters of an inch longer right eye first. Now if he holds the rings at the than the shorter, the astigmatism may be ignored, end of the rule, he will see them all blurred, and but where it is above that it ought to be corrected not appearing as so many distinct rings, but like by spectacles. An ordinary-sighted person, that one broad misty ring. Let him gradually slide the is, neither long nor short-sighted, may be so astig. paper nearer his eye, and he will find, when he has matic as to need spectacles to correct it. To test brought it to about 12in. from his eye, that the in this case, let the person get or borrow a pair of lines under 120 on both sides of the rings will spectacles of about 10in. focus, put them on, and appear tolerably distinct-in fact, will then just with these go through the testing I have before begin to be in focus; but the rings under 30° on described, and he will find they will enable each side will still appear to be misty. Now let him to put the lines somewhere on the rule him draw the paper nearer till these lines appear (we might appear more learned if we called as distinct as those under 120° were when at 12in. it an optometer), so as to be beyond distinct distance; now he will find that he will have to vision, and then by drawing them nearer he will reach 10in., thus showing that he has two foci to find the longest distance of distinct vision for some his right eye, and that they are at right angles to part of the lines, and the shorter focus for the one another. It can now be easily seen how much lines at right angles to the longer. If he be longthe difficulty is the eye has to labour under to get sighted, and therefore has to wear glasses, he must distinct vision, and how much the muscles of ac- get or borrow some deep glasses that will throw commodation have to do; for when any object is the lines out of focus towards the end of the rule, looked at, the eye tries its long focus, then finds and then he can begin to test himself, as before that does not give distinct vision for lines running described. Now, if opticians begin to know that in the direction of those under 308; then it the public are a little instructed in the matter they shortens its focus, and finds that it has lost its dis- will look it up more, and be ready to supply what tinctness for lines at right angles to the former is wanted. I found Mr. Ackland a very obliging ones; and so the eye is constantly vacillating gentleman, and I dare say he thought that, after between the two foci, and yet never finds rest; using the best tests he knew of, he had done the thus these muscles get tired, the eye feels fatigued, best he could for me in recommending me to ignore and the conclusion its owner comes to is that he my astigmatism, the fact being his tests were not has a weak eye; yet his eye is as strong as anyone's, delicate enough. But I would excuse, to a certain only it is astigmatic. Now let him test his left eye. extent, opticians, upon the ground that astigmatism He will find his first or long focus is 13in. for the has only been thought much of among them of late lines under 50° on each side of the circle, and 9in. years; but I think it is high time they all got up for the lines under 140° on each side, so that his to the present knowledge on the subject. And left eye is worse than his right, 4in. being the dif- then I find there is the optician's difficulty as well ference of the foci, and the longer focus being 70° as the public's; thus, an optician the other day from the longer focus of the right eye, and so with (who knew not astigmatic spectacles under that the shorter focus when compared with the shorter name, but as "peculiar-sighted spectacles," or focus of the right eye; now, we can easily under-cylindrical lenses"), said to me: "I hope you stand with two such eyes (for a pair they are not), will not go and blow up all the opticians in Enghow the outlines of objects are variously defined land in the ENGLISH MECHANIC, for there is the according as the eyes focus themselves, and how optician's side of the question to be looked the muscles of accommodation must be always on at as well as other persons; thus, persons the move and yet never find a resting-place. And come into my shop and want to be fitted ASTIGMATISM. it is further evident that the proper way to test for with spectacles in five minutes, and if, after I have astigmatism is to find these two foci, and not to put tried them on the optometer, and they cannot get a [18150.]-FROM further inquiries upon this sub- into the hands of the patient a number of lines pair of spectacles to suit them out of the lot that I ject, I am glad to find that opticians are begin-drawn in different directions, and asking him to know will be nearest to their sight, and I tell them butt, with ferrule and male screw, which I screw on to my small trout-rod when I desire to change it into a more powerful tool. B forms a gaff handle and camera-stand, and also carries a telescope clip. The gaff (or net) screws into a socket attached to the handle, like a bayonet to a musket. The gaff unscrews and a spike screws in to form an alpine stock. C is the gaff-handle, opened to form a stand for my pocket-camera. I am thus always prepared (with dry plates) to catch enormous fish with A, to land them with B, and photograph with C. C is not the best form of stand. It is better to have a small triangle, and have the three legs separate, with split ends to fasten on the triangle; but the hint is sufficient for any person wanting a thing of the kind to make it after the fashion he deems best. |