l62 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Mounting Infusoria. — I shall be glad if any one 

 can tell me a way of killing such Infusoria as vorticellae 

 and stentors, and such Animalcules as rotifers with 

 their cilia expanded, and then setting them up as 

 permanent objects. Saville Kent, in his recent work 

 on the Infusoria, says that a solution of osmic acid 

 effects this perfectly. I havetried it and failed totally. 

 At present I only have one per cent, solution (which 

 is the strength he recommends). Is the weakness of 

 the solution a cause of failure ? It certainly kills the 

 creatures very quickly, but yet not quickly enough. 

 But they seem to contract more in consequence of 

 the disturbance of the water caused by adding the 

 acid, than from the effects of the acid itself. Is there 

 any way .of applying the acid so as not to frighten 

 them by moving the water? Again, Mr. Kent 

 recommends osmic acid as a preservative. I have 

 set up half-a-dozen slides of non-contractile Infusoria 

 in this medium. After the lapse of a fortnight, they, 

 and the acid itself, are now the colour of ink, and 

 opaque. I cannot help thinking that Mr. Kent must 

 be mistaken in saying that osmic acid will preserve 

 animalcula — such as Eugleiia viridis — in their natural 

 colours. In Science-Gossip for 1879, Mr. G. du 

 Plessis says that a saturated solution of permanganate 

 of potash kills animalcula without contracting their 

 cilia. This solution is a very deep violet colour, 

 so deep as to be almost black. I have tried it, 

 but such things as vorticellre are quite contracted by 

 it. A certain T. C, later on in the same volume, 

 recommends "chromic oxydichloride" acid, com- 

 bined in certain proportions with permanganate of 

 potash. A querist asks in vain what this acid may 

 be, and when I enquired about it of a friend of 

 mine, a chemist, he had never heard of it. He 

 suggested that it might be chromic acid ; so I tried 

 this, but it was not of the slightest use. The 

 aggravating part is that these three "authorities," 

 S. Kent, G. du Plessis, and T. C., all say how 

 splendidly their methods succeed, whilst I follow 

 their directions as closely as I know how, and yet 

 fail so utterly that I feel sure that there must be some 

 "wrinkle " in the processes which their descriptions 

 do not make clear. If either of these people should 

 read this note, a little further information from them, 

 or from any one who has had better success than 

 myself, will be exceedingly welcome to II. M. J. 

 Underhill, Oxford. 



Improvements in Microscopic Slides.— I read 

 with considerable interest the paragraph p. 136, 

 "On Improvements in Microscopic Slides," and that 

 Mr. B. Piflfard had " obtained a patent specification 

 under the above title." I have been experimenting 

 upon a similar arrangement for some years past, my 

 first attempt was made in conjunction with Mr. 

 William Robson, about five years ago (then proprietor 



of the Lemington-on-Tyne Glass Works), The 

 primary object was to grind a level cell in the 

 ordinary glass slide with a sufficiently sunk margin to 

 allow a glass cover to be counter-sunk and flush with 

 the surface of the slide ; hence rendering leakage 

 impossible — simplifying, the process of mounting, 

 as there is no cell to build, and giving a perfection 

 and finish to the mount not otherwise attainable. 

 He found a difficulty in levelling the bottom of the 

 cell, as the tool used ground the edges more rapidly 

 than the centre ; this was to a considerable extent 

 obviated by an alteration in the grinding tool, but 

 the expense in working them became the most serious 

 difficulty — of course this vanishes if the principle is 

 applied to other material, vulcanite, wood, cardboard, 

 &c., which for opaque objects would be lighter, and 

 answer equally as good a purpose as glass. These 

 attempts were well-known to many members of " The 

 North of England Microscopical Society " (for which 

 I acted as honorary secretary up to the present 

 session), and to whom I was indebted for many 

 useful suggestions. — M. H. Robson, Newcastle-upon- 

 Tyne. 



Mr. Cole's " Studies." — Numbers 18 and 19 of 

 the welcome " Studies in Microscopical Science " 

 are devoted severally to "Vascular Tissue" (illus- 

 trated by Bast, sieve-tubes, and litter-cells), and 

 " Nerve of Horse " (the latter illustrated by an 

 exquisitely coloured plate). No. 9 of the "Popular 

 Microscopical Studies" treats upon the Crane fly 

 (Tipula), its life, history and general anatomy, 

 particularly the structure of the head. Part 10 of 

 " The Methods of Microscopical Research " continues 

 the subject of mounting, in which the student gets 

 the full benefit of Mr. Cole's long and very extensive 

 ■ experience. The first numbers mentioned above 

 were accompanied by sUdes, all of the usual neatness 

 and high finish, but that of the head of the Crane 

 fly is unusually beautiful, as it shows the compound 

 eyes and mouth organs very distinctly. 



"The Journal of the Royal Microscopical 

 Society." — The June number contains the following 

 papers : — " On the Estimation of Aperture in the 

 Microscope," by the late Charles Hockin, jun. ; 

 " Note on a Proper Definition of the Amplifying 

 Power of a Lens," by Professor E. Abbe ; " On 

 Certain Filaments observed in ^wr/r^/Za bifrons, '" hy 

 John Badcock. Besides the above we have the usual 

 excellent summary of current researches relating to 

 Zoology, Botany, Microscopy, &c. All the papers 

 are illustrated, 



Mr. J. E. Ady writes to say that owing to certain 

 differences betwixt himself and his colleague, Mr. 

 Hensoldt (which we cannot enter into here), he begs 

 the indulgence of the subscribers until suitable 

 arrangements can be made for continuing the 

 " Petrolofrical Studies." 



