June 1, 1899.] 



KNOWLEDGE. 



14,1 



of a one per cent, watery solution of rectified methylene-blue 

 and a one per cent, watery solution of eosin. 



At a recent meeting of the Royal ilicroscopical Society of 

 London, Mr. E. 'SI. Xelson exhibited a new objective by Zeiss, 

 called a " plankton-searcher," a low-power water immersion ob- 

 jective, designed for use in examining living objects in water. 



Vegetable fibres may be distinguished from animal fibres by 

 treatment with iodine and dilute sulphuric acid. The former 

 take a characteristic colour, either yellow or blue, while the 

 latter do not. The re-agents should be prepared as follows : — 

 Dissolve one part of potassium iodide in one hundred parts of 

 distilled water, and add an excess of pure iodine, so that the 

 solution shall always remain saturated. Mix one part of 

 distilled water with three parts of sulphuric acid, and, when 

 cool, add two parts of Price's glycerine. Both re-agents should 

 be kept in glass-stoppered bottles, and as they are liable to 

 change they should be occasionally tested on known fibres. 



These re-agents, appUed under the microscope, afford a means 

 of determining the species from which the fibre is derived. To 

 do this, some cells should be separated, extended on a glass slip, 

 and slightly moistened with glycerine. The length and breadth 

 may then be determined with a micrometer, and note should 

 be made, at this stage, of the shape and degree of taper of the 

 cells. Allow a small drop of iodine to flow under the cover, 

 removing any surplus with blotting paper. As soon as the 

 iodine has penetrated, apply the sulphuric acid in the same way, 

 carefully watch the results, and compare them with the action 

 of the re-agents on known fibres. 



A cheap and effective section-lifter may be made by hammer- 

 ing out flat the end of a copper wire of one eighth inch in 

 diameter and four inches long. The hammering should be done 

 on a smooth iron, and when it is of the requisite width it may 

 be trimmed with a pair of scissors and smoothed on a whet- 

 stone. 



The current issue of the Proceedings of the Eoyal Societi/ of 

 London contains a suggestive article by Miss Catherine Raisin 

 " On certain structures formed in the drying of a fluid with 

 particles in suspension,'' in which are described the many 

 interesting forms that the posvders of various rocks exhibit when 

 mounted in water and dried. These forms are classified, the 

 conditions and causes of theii formation are discussed, and 

 suggestions are made as to the possible explanation they afford 

 of the origin of many of the structni'al characters of rocks in 

 Nature. 



Excellent finishing varnishes maj' be made by well mixing on 

 glass artists' oil paint with gold size. Onlj' sufficient for 

 immediate needs should be mixed at one time. Sealing wax, 

 dissolved in alcohol, is also useful, but only the best wax should 

 be used, otherwise the varnish is liable to chip and leave the 

 glass. 



Dr. G. H. Bryan suggests, in the pages of the Journal of 

 Applied Microsrop'i, the following ingenious device for the more 



effective preparation of desmids, 

 diatoms, and other minute 

 mounting material. The re- 

 moval of all traces of acid neces- 

 sitates frequent washings and 

 decantations of the residues. It 

 is, therefore, important that the 

 vessel in which these operations 

 are performed should hang ver- 

 ti9all3'. otherwise much of the 

 residue rests against the sides of 

 the vessel and gets carried away 

 during the decantation. Dr. 

 Br3an gets over this difficulty by 

 suspending the test-tube by a 

 U-shaped piece of wire across the 

 base of which an india-rubber 

 ring is fixed. The test-tube is placed in the ring, the elasticity 

 of which aUows the tube to hang perfectly freely. The precipi- 

 tation of the diatoms is h;istened if the tube be set swinging 

 slightly. This device will also be found useful for washing and 

 collecting the insoluble residues of limestones and other rocks. 



Cross-sections of fibres may be obtained by glueing together 

 a mass of the fibre, bedding in paraffin, or by rolling them like 



a cigarette in a piece of sheet wax. When cut, the mass of 

 mixed sections is placed in benzole or alcohol, when the wax 

 soon floats on top and may be poured off. 



The following method of mounting in balsam on the cover, 

 and backing up with black varnish, will be found useful for such 

 objects as foraminifera, minerals, seeds, etc. Cement a thin 

 glass cover to a slip by applying a little balsam to the edge of 

 the cover, and accurately centre it on the turntable. Place and 

 arrange the objects on a thin coating of balsam in the centre of 

 the cover. When drv and set the objects may be completely 

 covered with balsam 'and put into the dry oven until hardened. 

 If the objects are white a layer of Brunswick black is now laid 

 all over the balsam ; if the objects are black white zinc cement 

 should be used. In either case care should be taken to lay them 

 on in thiii coats, and allowed to dry in the open air before the 

 next layer is applied. Xow remove the glass cover from the 

 slip by slightlv heating it. It may now be turned over and 

 mounted on the cell designed for it. Gelatine dissolved m 

 water, with enough alcohol added to liquefy it from the jelly 

 state, is a good preparation for fastening the cover to the cell. 



NOTES ON COMETS AND METEORS. 



By W. F. Desnixg, f.b.a.s. 



Swift's Comet (1899a).— During May this object proved an 

 extremelv interesting one. and was faintly visible to the naked 

 eye. It will continue favourably visible in June, though with 

 rapidly declining brightness. The comet will be situated in the 

 head of Draco on June 1st, and it may be seen about 1" south of 

 the fourth magnitude star J Draconis. On .June 8th the comet 

 will pass over the star v Herculus (magnitude 4-7), according to 

 the ephemeris by Moller in AM. Such., 3556, of which the 

 following is an abbreviation : — 



Date E.A. Distance in 



1«99' h m s. Dec. Millions of Sliles. Brightness. 



June"2 17 36 8 + SS"* 14' 53 1-34 



g IG 24 46 + 49° 35' 57 I'OS 



' 10 15 39 2 -f- 43° 2' 63 0-75 



14 15 9 57 + 36° 59' 71 0-53 



!', 18 14 .50 51 + 31° 49' 80 0-38 



Moonlight will then interfere, and at the end of June, when 

 our satelUte will have left the evening sky. the comet will have 

 practically travelled bevond the reach of ordinary telescopes. 



Tempel's Comet (1873 II).— The return of this comet is 

 now expected under favourable circumstances, and the following 

 ephemeris has been pubUshed by M. Schulhof, Ast. Xach., 



3554 : — 



Date E.A Distance in 



isw' h m s Dec. Millions of Miles. Brightness. 



June" 5 19 40 I'i - 4° 5' 55 1-27 



9 19 46 12 - 4" 25' 52 144 



"., 13 19 51 57 - 4° 54' 50 1-63 



„ 17 19 57 35 - S-' 33' 47 1-83 



„ 25 20 8 31 - 7° 23' 43 2-28 



The comet moves slowly eastwards in Antinous. 

 TcTTLE'.s Comet cannot be seen to advantage, as its position 

 will be near to, and south of the sun. 



Holmes's Comet is shortly expected, and Zwiers gives a 

 sweeping ephemeris in ,1s?. Xach., 3553. The brightness of the 

 comet is'steadily increasing. Its position at the end of .June is 

 close to A Arietis, forming a triangle with a and fi Arictis, but 

 it will become more favourably placed at a later period of the 

 summer. At the opposition of this comet in 1M92, about six 

 hundred obs&-vations were made, aftd the orbit has been 

 determined with considerable accuracy. Prof. Barnard, of the 

 Terkes Observatory, does not, however, regard the reapiiearance 

 of the comet as at all certain. He says : " The failure to see 

 the comet previous to its sudden apparition on November 6th, 

 1892, near the Andromeda Xebula, its uncometary apiJearance, 

 its peculiar freaks, and final, utter disappearance from the 

 heavens, connected with the nebulous appendage shown on the 

 photograph of November loth, woidd strongly suggest that the 

 object" was not a comet at all, but more probably a result of 

 some celestial accident. I think there is no question but this 

 comet will never be seen again, and doubtless before now it has 

 ceased to exist as an individual body" {Monthli/ Xotices, 1899, 

 March, p. 357;. 



