22 



KNOWLEDGE 



[jAsnAEY 2, 1899. 



and electrical science, like every other science, owes its 

 present position to the facts, and distortions of fact, pro- 

 pounded by the ancients. 



NOTES ON COMETS AND METEORS. 



By W. F. Denxixg, f.r.a.s. 



DiscovEKiES OF CoMF.TS. — The year 1808 forms a record as 

 regards the number of cometary discoveries and observations. 

 Altogether ten comets have been seen up to the end of November, 

 and of these three Tvere returns of the periodic comets of Pons- 

 Winnecke, Encke, and Wolf. Perrine has been the most 

 successful observer, having detected Pons-Wiunecke's comet as 

 well as three new comets. It is remarkable tliat two of these 

 bodies were accidentally found during the year by means of photo- 

 gi'aphy, viz : one by Coddington, on June 11th. and another, in 

 the Leonid radiant, by Prof. P. E. Chase, on November 14th. 

 It was a curious circumstance that a new comet should be jilaced 

 in a position within the sickle of Leo on the very date when a 

 meteoric shower was expected, and when scores of cameras 

 were directed to that jjarticular part of the firmament. The 

 wonder is that the comet was not independently detected by a 

 large number of observers. It passed its perihelion on September 

 19th, but at the opening of January, 1809, will be a little larighter 

 than on the date of its discovery, and situated about 8' north- 

 wards of the star S Leonis. On Januarj" 11th the comet will be 

 in R.A. lib. 8m. .and Dec. +."0° 32', while on January 15th its 

 position will be R.A. lib. 9m. and Dec. -|- SP 18'. 



Brooks's Comet. — Is now invisible near the snn, but will 

 probably be seen by observers in the southern hemisphere in 

 February. 



Wolf's Comet. — Is nearly stationary in Canis ilajor. On 

 January 5th the comet will be "Ji" west of the brilliant star 

 Sirius. 



The Leonid Meteop.s. — Though a brilliant display was far 

 from being realized, it seems that, at some stations, a tolerably 

 active shower was observed. At Alassio, on the Kiviera coast, 

 Mr. Hardcastle found the numbers remarkably coa,stant at 

 about thirty per hour. Prof. Young, at Princeton, U.S.A., 

 observing with Prof. Reed on November 15th, 3h. lorn, to 5 a.m., 

 counted about one hundred. There were about a dozen as 

 bright as stars of the first magnitude, and all of them left 

 .streaks. The maximum was at 3.45 a.m. (= G. M. T, 8.45 a,m.), 

 when for twenty minutes meteors appeared at the rate of two 

 or three a minute. The radiant was not well defined, but its 

 centre was nearly in 151'-' + 22^'-', At Rome fine weather favoured 

 the observations. At the observatory there on the night of the 

 13-14th, during about two and a half hours before midnight, 

 fifty-five meteors were counted, while in a similar period after 

 midnight, one hundred and four were seen. On the night of 

 the 14- 15th, during two and a half hours after midnight, one 

 hundred and twenty-sis meteors appeared, and of these thirty- 

 six were of the first magnitude and thirtj'-six of the second 

 magnitude. Twenty-six left trains. The total period of 

 observation during the several nights was lib. 38m., and the 

 aggregate number of meteors seen four hundred and eighty-six. 

 The work was distributed amongst nine observei'S, who divided 

 the watches on .successive nights, but it is not stated how 

 many of these were looking out at the same time. The recent 

 observations, coming from different quarters, are singularly 

 discordant as to the number of meteors visible. At some jilaces 

 no meteors appear to have been seen, whUe at others a 

 well defined and somewhat numerous display of Leonids was 

 witnessed. 



The Bielid Meteors. — In England cloudy weather and 

 moonlight effectively veiled all traces of this shower. It is 

 highly probable that it quite failed to return in the strength 

 expected, and that, even had clear skies permitted full observa- 

 tion, the results would have been negative. The period of 

 thirteen years is evidently too short for maximum returns of 

 the shower. It may furnish some meteors on November 23rd, 

 1899, and ought to give a very brilliant display on about 

 November 17th, 1905. 



The QuADR.iNTiDS, — Many of these meteors are likely to be 

 visible on the evening of January 1st, and the morning and 

 evening of January 2nd. The best time to look for them 

 will be before moonrise on the early mornings of the dates 

 mentioned. 



iHirvosropp. 



John H. Cooke, f.l.s., f.g.s. 



No one, probably, has done more towards increasing our 

 knowledge of the nature and disposition of the cell contents 

 of diatoms than Pfitzer. One of the difficulties that that 

 distinguished worker experienced in the study of his subject 

 was the differentiating of the fine colourless plasm in the plasm 

 sac. This was chiefly due to the fact that the refractive index 

 of the plasm differed but sligbiy from that of water. To over- 

 come this he suggested the apphcation of dilute hydrochloric 

 acid. The result, happilj-, was the immediate shrinkage of the 

 plasm sac and the disclosure of its structure, A one per cent, 

 solution of osmic acid has been found to be even more effective, 

 as it not only has an effect on the plasm sac similar to that of 

 hydrocldoric acid, but, by changing the oil globules, that are 

 invai'iably present in the cells, to a black colour, it enables the 

 worker to readily study the relations of the various matters 

 that make up the cell-contents. 



It is well known that, other things being equal, the higher 

 the refractive index of a mounting medium the more effective 

 is the medium for microscopical manipulations. The mounting 

 fluids most commonly used are — oil of turpentine, refractive 

 index, 1'475 : castor oil, 1'49 : Canada balsam. 1'549 : oil of 

 cloves, I'Ooo; balsam of tolu, l't)2S ; and oil of cassia, 1-641, 

 It may be of interest to microseopists to have their attention 

 drawn to a little known, but effective mixture, having a refrac- 

 tive index as high as 2-40, which was discovered by Prof. 

 Hamilton Smith, of Rochester. The mode of preparation is as 

 follows : — In tw-o fluid drams of glycerine jelly, made in the 

 usual way, dissolve, in the cold, ten drams of chemically pure 

 stannous chloride. When solution is complete boil for a few 

 minutes, and filter while hot. When mounting place a drop on 

 the slide and heat in the usual way. The difference in the 

 appearance of diatoms mounted in this medium and in other 

 fluids must be seen to be appreciated. 



In the Journal of Applied Micmsrojiy, Mr. G. H. French 

 describes the method that he adopts for imbedding and staining 

 lichens. He recommends the immersion of the lichens in ninety- 

 five per cent, alcohol for twenty-foui- hours, after which they 

 should be placed in thin and thick collodion, alternately for 

 another twenty-four hours. After imbedding in thick collodion, 

 and hardening in seventy per cent, alcohol, the sections are cut, 

 and stained with borax-carmine. The fungus part of the 

 lichen will, after this treatment, acquire a pale pink hue, while 

 the algal cells acquire a greenish-red shade. By this method 

 the host cells may be readily distinguished from the fungus. 



At a recent meeting of the Quekett Club, Mr, Goodwin gave 

 the results of his experiments in illuminating microscopic 

 objects without the aid of a bull's-eye condenser. Under 

 ordinary conditions the lamj) has to be placed at a distance of 

 about eight inches from the back of the condenser in order to 

 secure the best effects. By ]ilacing a plano-convex lens, of five- 

 inch focus, in the screen-holder of the condenser, he has been 

 enabled to bring the lamp to w-ithin three inches of the back of 

 the combination, thus obtaining better illumination and defini- 

 tion, a matter of considerable importance when high powers 

 are used. It is a simple and effective contrivance, and is worthy 

 of the attention of those who desire to make the best use of 

 theh- appliances. 



There is no better cement for general •• mounting'' purposes 

 than old gold size. The older the better for the ])urposes of 

 the microscopist. Gold size is, in reality, nothing but good 

 linseed oU rendered very drying by the usual methods. It has 

 manj' advantages over damar, asphalt, and the many other 

 cements on the market, as it may be laid on readily and quickly 

 in successive coats, and, though it mixes with turpentine, it is 

 unaffected by it when once hard and dry. The cement should 

 be prepared in smaU quantities, and in the following manner : — 

 Take a small quantity of old gold size, thin it with turpentine, 

 and work in enough lamp-black or aniline dye to colour it. This 

 will dry tough, and with a beautiful gloss. If a ring of shellac 

 varnish be made round the edge of the cell, and, when dry, this 

 cement be applied in a succession of coats as a " finish," the 

 microscopist will have a mount which, with fair usage, will 

 last for years. 



