88 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Mounting Starches. ^ — Few objects when viewed 

 by polarised light are more lovely than the starches. 

 They are generally mounted in the same way that 

 algae, mosses, <S;c., are prepared for examination, 

 viz., by placing a small quantity on a slide and then 

 applying the balsam ; but if the following method be 

 adopted slides may be obtained, which, for freedom 

 from air bubbles and the even distribution of the 

 component particles, cannot be surpassed. Pour 

 into a test tube a sufficient quantity of Canada 

 balsam to mount as many slides as may be required, 

 and heat over the ilame of a spirit-lamp. When the 

 balsam becomes thin, dredge into it, through muslin, 

 the starch to be mounted. The air bubbles which 

 will then appear must be caused to burst, eitlier by 

 .again heating the balsam, or by diluting it with 

 turpentine. The starch may then be mounted by 

 taking up a small quantity with a dipping tube and 

 placing upon a glass slip, and covering with a thin 

 circle or square previously warmed. I have never 

 seen this mode described in any work, it being my 

 own ; but I am sure if those who study the science of 

 microscopy will give it a trial, they will use it in 

 preference to any other. — A. J. D. 



Preserving Fluid. — Having been engaged in 

 examining and preserving animalcula, I find the 

 following fluid keeps and instantly kills all living 

 species, so as to preserve the natural and life-like 

 forms : 25 grains of alkaline nitrate of chlorine, 

 10 grains cobalt chloride (this preserves the green 

 colour), 15 grains of aniline com., 15 grains of spirit 

 of wine, 2 grains of carbolic acid, 40 grains of dis- 

 tilled water. Shake and filter ; keejD in well-stoppered 

 ■bottle.— 7?. Atkins, F.R.M.S. 



A new Vivarium.— Mr. J. D. Hardy has intro- 

 duced a new vivarium to the members of the Quekett 

 ■Club, the particulars of which will be published /;/ 

 extenso in the Quekett Club journal. It consists of 

 one or more indiarubber rings cemented on to one 

 piece of glass, which is then covered with another 

 piece, and the whole is held together by springs, 

 either of indiarubber or steel. It is made to be quite 

 watertight, and the vivaria will be obtainable of Mr. 

 Stanley, of London Bridge, Mr. Hardy has recently 

 written to us as follows : "My attention has been 

 called to a 'live cell' very similar to mine in 1879 

 (p. 38) . I was quite ignorar.t of this when I contrived 

 mine, but it will be found on comparison that the 

 I .0 cells have quite different uses. Mr. A. Smith's 

 is nothing more thin a compressorium, whereas 

 mine is realy a ' live cell,' growing cell if you like, 

 as the object can be placed in a beaker of water and 

 kept alive the same as in the ordinary trough. I can 

 see at once — from experience — that Mr. A. Smith's 

 cell is almost useless, as filling the cell before putting 



on the cover glass would completely disarrange most 

 objects. My vivarium combines many other uses not 

 to be found in any other arrangement that I know of. 

 It is but right that you should be made acquainted 

 with this fact (the similarity of construction), in any 

 comment you might make. I am, however, quite 

 content to let it live or not on its merits." 



The Crust on Teeth.— The soft, white, pap- 

 like substance, which collects about the roots of the 

 human teeth, is seen under the microscope to consist 

 chiefly of immense numbers of rod-like filaments. 

 What are these '>.—E. J. W. 



Dullness in Objectives. — I think the dullness is 

 caused by what is termed "sweating." That is to 

 say, certain kinds of glass are always covered with a 

 film of moisture on exposure, i.e., they appear to be 

 hygroscopic and in time lose their lustre. The defect 

 is to be attributed to an imperfect composition of the 

 glass. J. H. Dallmeyer, F.R.A..S., in an article on the 

 subject says, " I would remark that in our present state 

 of knowledge glass may be described as a mechanical 

 mixture, i.e., a silicate of at least two metals belonging 

 to different groups, one of which must be an 

 alkaline metal ; and there can be no question that the 

 nearer these ingredients approach atomic proportions 

 the better is the resulting glass." But the point of 

 saturation of the silicate varies with the temperature 

 of the furnace, and hence it results that no two pots, 

 even of optical glass, are precisely alike in composition. 

 To ascertain the defect of sweating it is only necessary 

 to wipe a glass, then to expose it in a comparatively 

 even temperature in a room, and observe whether 

 after the lapse of a few days the passing a finger 

 across it indicates a film of moisture. — E. A. Broivne. 



Mr. Bolton's "Portfolio."' — We are pleased 

 to acknowledge the receipt of the now well-known 

 " Portfolio of Drawings," containing descriptions of 

 the living organisms (animal and vegetable) illustra- 

 tive of Freshwater and Marine Life, which have been 

 sent out with the living specimens by Vi\. Thomas 

 Bolton, F.R.M.S., of 57 Newhall Street, Birmingham. 

 It contains well-executed plates, and good descrip- 

 tions of the following : in the vegetable kingdom — 

 desmids and diatoms, yEcidiuiii iirtica, Zygoiteiini 

 cniciata, Valtisiicria spiralis. In the animal kingdom 

 — Acineta, Deiidrosonia radians, Choano-flagellata, 

 Bnrsaria truncatclla. Marine infusoria — Nassiola 

 ornata, Spirostoinuni teres, Cordylophora lacnstris, 

 Lnccrnaria auricula, &c. &c. 



Floscularia, &c.— From a pond in this neigh- 

 bourhood (Canterbury) I procured last week some 

 beautiful specimens of Floscularia campanulata. One 

 of the creatures has ova in a very advanced stage 

 of incubation. I found them adhering to some Nilclla 

 flcxilis. Is not this remarkable, considering the time of 

 year and severe weather we have ? — Tom B. Rossctcr. 



