46 



KNOWLEDGE. 



[Februaby 1, 1900. 



use of an upright apparatus is the best, but it is open to many 

 objections, chief among which are its instabilit}', the- difficulty 

 of focussing, and the fatigue it occasions the operator. Mr. 

 Brightman, Colston Street, Bristol, has deyised a useful and 

 substantial support (see Fig.), which overcomes these difficulties, 



EUvatjtfit' 



^y//.'.''J;iM 



Sojck 'Vtjci\- 



and enables the photographer to successfully operate with his 

 apparatus at an angle of 45'' to the vertical. The arrangement 

 is a good one, and is already in use in medical circles in Bristol. 



One important habit which the microscopist should cultivate 

 is that of making copious notes of observations. He .should 

 never be without his memorandum or note book. No more 

 profitless work can be imagined than collecting natural history 

 specimens and material without some specific aim or object. 

 Every observation made should be carefully recorded, and the 

 date of capture, locality, and, where possible, the food-plant, 

 should always be attached to the specimens when these are 

 mounted. For field memoranda the use of a stylographic pen 

 is advisable, as pencil writing is apt to rub and efface in time 

 by the motions of the body. A larger record book for more 

 extended notes should be kept at home for biological details. 

 When studying insects, for instance, notes on adolescent states, 

 which it is intended to rear to the imago, cannot be too carefully 

 made, or in too much detail. The relative size, details of 

 ornamentation and structure, dates of transformation from one 

 state to another — indeed everything that pertains to the 

 biography of the species — should be noted down, for where 

 exact data are so essential, little or nothing should be trusted to 

 mere memory. 



In photographing wood sections without a lens, Herr Fomm 

 places a piece of tinfoil on one side of the section and the film 

 surface of a piece of bromide paper against the other side. A 

 good impression — showing clearly the rings and rays of the 

 wood — is produced in about a half a minute when a metallic 

 point negatively charged by an influence machine is brought 

 within two inches of the paper. It is explained that the paper 

 becomes negatively charged, and a photographically active glow- 

 light is produced between it and the wood. It is proposed to 

 try this method for copying drawings and for other purposes. 



Mr. F, E. Rowley gives some valuable hints on the collection 

 and preservation of diatoms in a recent issue of Natural 

 Science. In collecting, a spoon attached to a stick may be used 

 for skimming the brown diatomaceous ooze off the surface of 

 the mud ; a drag net serves this purpose in the case of forms 

 occurring at greater depths, e.g., Surr/rella. The latter should 

 be placed with water in shallow glass vessels sheltered from 

 direct sunlight. The diatoms will appear in masses on the sur- 

 face of the mud after twelve hours. Transfer them by means 

 of a pipette to the fixing fluid. Fleming's chromo-aceto-osmic 

 acid, and sublimate, in aqueous or alcoholic solution, is recom- 

 mended as being the best reagent for demonstrating the delicate 

 structural features of the nucleus and cytoplasm during 

 division. The chromatic elements of the nucleus are well 

 shown by picro-sulphuric acid followed by hematoxylin. The 

 arrangement of the cytoplasm, the chromatophores, and other 

 inclusions in the cell may be well brought out, in unstained 

 preparations, by a one per cent, osmic acid solution. A solu- 



tion of iodic alcohol (45 per cent.) is recommended for the study 

 of the so-called " red granules " of Biitschli, which, by the fore- 

 going method, stain well after fixing. 



Large forms receive a somewhat different treatment. They 

 are removed individually with the aid of a capillary tube and a 

 dissecting microscope, and are transferred to the filing bath. 

 The solution is decanted oil after fifteen minutes and the objects 

 are passed through water and alcohol, of strengths increasing to 

 the absolute point. This extracts oil and the colouring matter 

 of the chromatophores. The preparation is then passed through 

 alcohols of decreasing strength into distilled water, after which 

 it is stained in a weak solution of Delafield's haematoxylin. 

 The material is then passed .successively through 35, 70, 95 per 

 cent, and absolute alcohol into clove oil and finally mounted in 

 dammar. 



[All communications in reference tn this Column should be 

 addressed to Mr. J. IT. Cool-e at the Office of Knowledgk.] 



NOTES ON COMETS AND METEORS. 



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



No new comet has been discovered during the last three months. 

 Giacobini's comet (first seen on September 29th, 1899) is now 

 invisible, and Holmes's comet some time since passed beyond 

 the range of ordinary instruments. An ephemeris by Zwiers is 

 given in Ast. Xach. 3610, and from this it appears that the 

 position of Holmes's comet on February 5th, 1900, will be 

 R.A. 2h. 40m. 40s., Dec. -f 39'^ 14 37 , or about 5 degrees 

 west of R Persei (Algol). 



Fini.ay's Comet. — This object was discovered in September, 

 188G, at the Cape of Good Hope, and it was soon found to be 

 moving in an elliptical orbit, with a period of little more than 

 six and a-half years. Mr. Finlay redetected the comet in July 

 1893, and it is now again near its perihelion, but M. Schulhof, 

 of Paris, has recently investigated the orbit, and finds that the 

 comet is not likely to be seen before 190(5. In August of that 

 year it will be comparatively near to the earth, the distance 

 separating the two bodies being less than 20 milhons of miles. 



The Shower of Leonids in 1899. — The comparative 

 deficiency of meteors at the middle of last November has led to 

 the suggestion that the ])Osition of the stream may possibly 

 have been disturbed by jilanetary attraction. Though this 

 particular shower has been irregularly providing us with briUiant 

 displays during the last thousand years, there is certainly evidence 

 to show that the meteor-group has been sufficiently disturbed to 

 enable it to pass almost clear of the earth. From computations 

 undertaken by Dr. Downing and his assistants at the Xautical 

 Almanac Office, it apjiears that the large planets Jupiter 

 and Saturn have exercised considerable influence upon the orbit 

 of the swarm which visited us in 1866, and that at its return in 

 1889 it must have passed about l,300,o00 miles inside the earth's 

 orbit. Next year the conditions wiU be still more unfavourable, 

 whence, if the theoretical deductions are quite rehable, there 

 wiU be a poor display, unless the meteors are richly dispersed 

 in a direction away from the sun. Indeed, the opinion seems 

 gaining ground that the shower is practically lost to the present 

 generation of observers. There is, however, sufficient doubt in 

 the matter to encourage the hope that the meteors may reveal 

 themselves either in 1900 or 1901, and particularly in the latter 

 year. There was a fine display in 1868, though it was little 

 expected. We have perhaps, in recent years, regarded our 

 prospects of witnessing a bright reappearance of the phenomenon 

 in too favourable a light, when all the circumstances are con- 

 sidered. At a single station the chances are always great that 

 the shower will escape observation. During the last thousand 

 years very few brilliant rettu'us have been observed in England. 

 Historical records do not furnish descriptions of showers in 

 1833, 1799, 1766, 1733, or in many previous years when the 

 Leonid comet was probablj' near its perihelion. Had the event 

 occurred some mention ot it would certainly have been pre- 

 served. But notwithstanding prevalent doubts, and the failure 

 of recent attempts, we should redouble our efforts to witness 

 the shower in the two or three ensuing years, for even should 

 it fail to present a conspicuous as]iect, it will be possible to 

 obtain negative evidence of a useful kind. It must be remem- 



