46 



KNOWLEDGE 



[Febbdart 1, 1899. 



Glyceriue is one of the most useful presei-yative media for 

 microscopical manipulations. Pure glycerine should not, how- 

 ever, be used, as confervoid growths are apt to appear in it. To 

 obviate this, the addition of about two per cent, of camphor 

 water is recommended. 



In a paper read at the last meeting of the American j\Iicro- 

 scopical Society, Mr. B. D. Myers embodied the results of a 

 series of experiments that he has conducted in the histologic 

 laboratory of Cornell University on the uses of picro-carmiue 

 and alum carmine as counter stains. With hematoxylin the 

 picro-carmine gives a more differential stain than picro-fuschin, 

 and shows the characteristic alkaline re-action with hematoxylin, 

 bringing out the hematoxylin as a beautiful sharp blue, while 

 the acid picro-fuschin tends to fade it. 



The Canada balsam of commerce is frequently contaminated 

 with impurities, and is therefore not always suitable for 

 mounting purposes. These impurities may be eliminated by 

 filtration in the following manner; — Make a cone of Swedish 

 filter paper, and affix to the outside of it, at equal distances 

 apart, three short lengths of glass tubing. On placing this 

 apparatus in a glass funnel of suitable size, the tubing will 

 prevent the filter paper touching the sides of the funnel. 

 Dissolve the balsam, which is to be treated, insufficient benzole 

 to make a mixture of a thin, syrupy consistency. Pour this 

 into the filter, and to prevent evaporation cover the funnel with 

 a greased glass plate. The filtered balsam should be put on one 

 side until the benzole has evaporated sufficiently to allow of its 

 being used. 



To preserve microscopic organisms intact, it is necessary that 

 they should be mounted without crushing, flattening, bleaching, 

 or contorting their parts — that is, the organisms should, after 

 the preliminary stages of preparation, be mounted in a medium 

 of suitable density, and "without pressure." The following 

 medium — viz., absolute alcohol, three parts : glycerine, two parts : 

 and distilled water, one part — will be found to give very 

 successful results with hard ova, zocea, the young of Crustacea, 

 and most insects and plants. The specimens, which should be 

 quite fresh, ought to be dropped into small tubes containing 

 the above mixture, and allowed to remain there for any period 

 varying from three to twelve months. Should the fluid become 

 discoloured, decant it, and replace with a fresh supply. "When 

 ready, the specimens must be placed in a cell containing the 

 fluid in which it is intended they shall be mounted. The com- 

 position of this may be six parts of distilled water and one part 

 each of glycerine and alcohol, or such other proportions of these 

 constituents as may be best suited to the object to be mounted, 

 provided that the density of the mountant be less than that of 

 the fluid which was used in the preparatory stages. This method 

 of preparation has been successfully tested in marine biological 

 laboratories both at home and abroad. 



Microscopists, who have occasion to do much work with the 

 camera-lucida, will find the following device of considerable 

 assistance in their microscopical sketches ; — Take a circular cover 

 glass, rule it in squares, and drop it in the eye-piece so that the 

 squares may be seen crossing the field of view in which the 

 object has been placed. By carefully transferring to squared 

 paper the observations obtained, a satisfactory and effective 

 drawing of the object may be made. Mr. G. C. Karop suggested 

 to the members of the Quekett Club the following method for 

 etching the squares on the glass cover glass : — Cement the circle 

 to a glass-slip, cover it with a thin coating of paraffin wax, and 

 rule the squires required with a fine-pointed needle. Mix a 

 small quantity of finely-powdered fluor-spar and concentrated 

 sulphuric acid in a platinum crucible, heat the mixture, and 

 allow the resulting fumes of hydrofluoric acid to play on the 

 squares of the glass circle. The etching will soon be effected, 

 after which, clean the glass and mount it in a circle of card- 

 board. 



Bujwid was the first microscopist to systematically study the 

 germ life contained in hailstones. The subject has now been 

 taken up by Mr. C. F. Harrison, of Guelph, who has isolated 

 and determined a series of bacteria and moulds, two of which, 

 B.fiavus grandinis, and M. melleus cirandhiis, are new to science. 

 He has published a monograph on the subject, in the course of 

 which he describes the methods that he adopted. The hail- 

 stones were washed in a mercuric chloride solution (one in five 

 hundred), rinsed several times in sterilized cold water, and each 



stone thus treated was dropped into a tube of melted nutrient 

 gelatine. The mixture was then thoroughly shaken, and the 

 plates made in the usual manner. Pour days afterwards the 

 plates were counted, all the bacteria and moulds were isolated, 

 and their cultural characteristics determined. The results have 

 led him to support Bujwid's theory, that surface water is carried 

 up by storms and frozen, producing hailstones. 



NOTES ON COMETS AND METEORS. 



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



Brooks's Cojikt (discovered October 20th) is now invisible to 

 observers in this country. At the middle of February the comet 

 will be situated in Corona Australis, and very faint, for its dis- 

 tance from the earth will be about one hundred and ninety 

 millions of miles. 



Ch.'VSe'.^ Comet is favourably placed as regards its position in 

 the heavens, but is too difficult an object to be seen in ordinary 

 telescojjes. The following is an ephemeris for Berlin midnight, 

 by Moller {Ast. Nack, 3531) :— 



Dist.ance ill 

 R.A. Decimation. millions of Bright- 



Date, h. m. s. o / miles. ness. 



Februarv 4 ... 11 7 48 H-35 1 174 102 



8 ... 11 6 23 35 40 175 99 



12 ... 11 4 42 36 15 176 96 



16 ... 11 2 47 36 47 178 092 



The comet is therefore receding from the earth and gradually 

 becoming fainter. 



Periodical Co.mets due in 1899. — A considerable number 

 of these interesting bodies are expected to return to perihelion 

 during the present year. Denning's Comet (1881 V.) is due in 

 Febru.ary. Temgel's Comet (1866 I.), which deserves particular 

 notice from the fact of its close association with the Leonid 

 meteors, should return in the spring. Barnard's comet (1892 V.), 

 Tuttle's (I85S I.), and Holmes's (1892 III.) is expected in 

 Ajiril or May, while Tempel's comet (1873 II.) should be seen 

 in July. The latter comet ought to be well displayed at this 

 return, for the conditions are nearly the same as in 1873 (five of 

 its periods of 5'20 years being equal to twenty-six years), when 

 the comet was on the same side of the sun as the earth. 



The Leonid Meteors. — Reports of observations continue 

 to come in, but some time must yet elapse before a complete 

 summary of all the results can be compiled. American observers 

 appear to have been the most successful, but a really brilliant 

 shower was not observed anywhere. Prof. Payne, at Northfield, 

 jMin., watched on November 14th, r2h. 80m. to 15h. 45m., and 

 counted eighty-one meteors, nearly all of which were Leonids. 

 Mr. H. R. Smith, at Philadelphia, counted seventy-six meteors 

 between r2h. 20m. and 16h. 40m. on the same night. Prof. 

 Landis, at Carlisle, Pa., reports that on November 14th, between 

 12h. and 13h., thirty-four meteors were counted ; between 13h. 

 and 14h., sixty-four ; and between 14h. and 14h. 30m., fifty-four. 

 Four to twelve observers were engaged, and he judged that the 

 average hourly number from one hundred to one hundred and 

 twenty-five. At Northfield, Min., two meteor trails were 

 photographed. Prof. Wilson describes them as perfectly straight, 

 and lines drawn through the two intersect at 151'5'' -|- 22'3''. 

 This is in remarkable agreement with the place of the radiant 

 as determined by four trails photographed at Harvard College, 

 which nearly intersected at the point R.A. lOh. 6'8m. Dec. 

 + 22° 16'. This accordance encourages the hope that, though 

 the recent shower was less brilliant than expected, photography 

 has fully justified its employment, and furnished us with the 

 place of the apparent radiant with a high degree of accuracy. 

 He says, in summarizing the American observations, that on the 

 morning of November 15th the probable horary rate of Leonids 

 for one observer watching the sky continuously was about forty. 

 This shows a great increase of strength as compared with 1896 

 and 1897, but the most singular result is that the radiant was 

 found to be nearly two degrees south of the average position 

 (149^ 28' -f 22° 52') indicated by observations during the 

 previous sixty-five years. 



At the Yei'kes Observatory, Prof. Barnard had a clear sky 

 shortly after midnight on November 14th, and watched until 

 daylight. He saw several hundred meteors, many of them being 

 of the first magnitude, and a few brighter. They left bluish- 

 green streaks. The maximum was reached between 3 a.ni. and 



