1900] MICROSCOPICAL JOURNAL 59 



gum dammar in benzole. Select a clean sample of the gum 

 and dissolve in benzole until the required consistency is 

 reached. The edg-e of the cover-glass is then freed from 

 superfluous mountant, and the cement laid on in the usual 

 way. The first layer will in a few hours be sufficiently set 

 for the application of a second, which is generally neces- 

 sary. 



Mounting Algae. — Boil some water for ten minutes to get 

 rid of the air in it, and in this gently heat or even boil the 

 specimen itself, for an other twelve or fifteen minutes, and 

 finally put the latter under the air pump in a very small 

 quantity of the same water. Before mounting in glycerine 

 jelly, soak in a mixture of glycerine and water, and exam- 

 ine under a dissecting lens. If any air-bubbles should still 

 remain in the cells they must be removed carefully one by 

 one with a tine needle. It is useless putting the slide un- 

 der the air-pump when mounted — glycerine jelly sets and 

 cools too quickly,and is besides too dense to displace the air 

 in the cells. The object needs the above careful prepara- 

 tion beforehand. Glycerine jelly is always more trouble- 

 some than Canada balsam with respect to air bubbles, but 

 is otherwise very suitable for botanical mounting. There 

 is no book which will enable one to identify algae off-hand, 

 without a preliminary study of the subject, but I would 

 suggest obtaining "Gray's British Seaweeds" or Harvey's 

 "Manual of British Marine Algae." The authoritative book 

 on Marine Algae is Harvey's "Phycologia Britannica," but 

 it is very costly ($37). M. C. Cooke's "British Freshwater 

 Algae" is the best book on the sister subject. 



Micrometers. — Some method of measuring objects will 

 be required, and the simplest means of doing- this is to be- 

 come possessed of a stage micrometer, which is a slide 3 in. 

 by 1 in. ruled in l-100ths and l-1000ths of an inch, or l-10ths 

 and l-100ths of a millimetre, and costing $1. A small disc 

 drops into the Huygenian eyepiece, and lies on the dia- 

 phragm. This is called the eyepiece micrometer, and it is 

 also ruled with divisions that generally bear some relation 

 to an inch or millimetre scale. This also costs $1.25. To 



