110 



HAUDWICKE'S SCIENCE-GOSSIP. 



again. The hairs of the Pekan, one of the Weasel 

 family, said to be found in Canada and the Northern 

 States of America, are curious for the structure o^ 



Fig. 71. Hairs of Pekan : A, large hairs ; B, small ditto. 



the leaf-like cells or scales that surround the interior 

 of the hair. The others are too well known to 

 require further notice, and are only added for the 



Fig. 72. Hair of Tiresias 

 X 120. 



Fig. 73. Hair of Grey Fox 

 X 120. 



sake of comparing their relative sizes. I find 

 Canada balsam and chloroform an excellent prepa- 

 rations for the preservation of animal hairs after 



they have been cleaned in po'ash or soda; and 

 many of them form beautiful polarizing objects. 



R. H. NisBETT Browne. 



" Life has been the medium through which the 

 geological history of the past is connected with 

 the' unknown future," — Taylor's "Geology of Man- 

 chester." 



MICROSCOPY. 



DapvK Lines, ^&c.— In reply to the inquiry of 

 " G-. W.," I may say that I at first experienced the 

 same difiiculty in obtaining a good definition with 

 the binocular with any power over an inch objective, 

 and that I found a Webster condenser remedied 

 the dark line he speaks of, and enabled even a low- 

 angled 4-lOths to be used with comfort ; also that a 

 cap lens of crown glass of meniscus form, with a 

 central stop, using also a small central stop in the 

 diaphragm of the condenser, enabled me to get a 

 dark ground illumination with the 4-lOths, superior 

 in illumination and definition to the parabola. — 

 /. W. Meachen. 



Impekfect Mounting.— I have a few slides, 

 mounted I think about twenty years ago, which 

 should contain spiculse of Ilolotlmriadce, but whicli, 

 owing to improper manipulation or unsuitable 

 medium, do not now show the least trace of any 

 organism. The slides, from their neatness, seem to 

 be the work of a professional mounter. I am, how- 

 ever, much puzzled to know what the mounting 

 medium is. It is now quite yellow, and on removing 

 one of the covering glasses I find it still soft, but, 

 unlike balsam, it is elastic, and does not melt with 

 heat. It smells somewhat like, and has all the 

 appearance of, common glue. As it is a matter of 

 very great importance to microscopists, I should 

 much like to know the cause of the objects disap- 

 pearing. Also whether any fellow-workers have 

 noticed the same effect on calcareous spicul£E by 

 balsam, as a few slides that 1 examined a short 

 time since, although recently mounted, show 

 serious symptoms of decay, the fine points having 

 in some cases entirely disappeared. In the case of 

 the slides of Holothuriadse referred to, the loss is 

 much to be deplored, as they were all preparations 

 of exceedingly rare species, some of them indeed 

 being marked type specimens. — W. Swanston. 



Mounting in .Damak. — I have mounted a great 

 many things of late in tlie new substitute for 

 Canada balsam, — gum-damar. It is very handy, in- 

 asmuch as it requires no previous warming. But 

 I can make little use of it, as bubbles frequently 

 rise, and are apparently difBcult to break. I 

 know not whether any of the readers of Science- 

 Gossip have been more successful. If any one 

 should ask me which I prefer, I should decidedly 

 say Canada balsam. I wish the damar could be 

 brought to more use, as it is undoubtedly much 

 simpler to work with. — W. S. Palmer. 



Mounting Diatomace^. — ^Diatoms, when ar- 

 ranged loosely on a slide, are almost certain to be 

 thrown into confusion by the wave of balsam, in 

 whatever manner it may be applied. If, however, 

 the centre of the slip, or, preferably, the thin glass 

 cover, be first smeared with a thin mucilage of gum 



