160 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Another method, suggested by Mr. Atwood, of Chicago,* also 

 gives most excellent results. It is as follows : — 



" For mounting marine algae I prepare an artificial sea- water by 

 dissolving in rain or distilled water a sufficient amount of sea-salt, 

 which can be procured of any druggist. The dried algse immersed 

 in this will, in an hour, have resumed their original state. When 

 this has occurred I pick out and clip off such pieces as are best 

 adapted for mounting, transfer them to a bowl of distilled water, and 

 wash them clean. They are thence transferred into a saturated solu- 

 tion of salicylic acid. The slides are prepared for receiving the 

 mounts, with cells made of bleached shellac dissolved in Cologne 

 spirits, thoroughly dry. The specimen is removed from the salicylic 

 solution and arranged in its place, and the cell is filled with the 

 salicylic solution. The cover-glass, first breathed upon, is put into 

 its place, the surplus fluid removed in the usual way, and the cell 

 closed with a thin coating of gold size. In a day or two I lay on 

 more size, and when it is dry finish off with zinc cement or Brunswick 

 black. 



In mounting an alga having Isthmia parasitic upon it, I have 

 found it almost impossible to fill the diatoms if balsam be used, 

 whereas the salicylic solution fills every valve and cavity. The acid 

 sometimes, but not often, decolorizes the algse. The immersion of 

 marine algee in the artificial sea-water is an important point that 

 should not be neglected, as otherwise their full beauty cannot be 

 brought out." 



Preparing thin Sections of friable and decomposed Rocks, Sands, 

 Clays, Oozes, and other Granulated Substances.f — ^Mr. F. G. Pearcey 

 describes the method adopted in the case of some of the ' Challenger ' 

 collections, transparent sections of which were required, but which it 

 was impossible to prepare by the ordinary method of the lapidary's 

 •wheel on account of their friability. It was therefore necessary to 

 find some method of making them hard and compact, so that they 

 could be subjected to this process. The principle of the method 

 consists in the introduction of some foreign substance to cement the 

 grains together, and make the material hard and compact. This 

 is carried out by soaking in a solution of gum copal in ether, and 

 then evaporating the ether, a method which is in use by naturalists 

 for making sections of the hard parts of Echinoderms. 



Preparation and Use of tlie Cement. — The first process consists in 

 preparing a solution of gum copal in ether. Take one half-pound 

 of the best gum copal and place it in a strong glass jar, sufficient to 

 hold about one quart, with finely ground air-tight stopper ; add about 

 20 ounces of ether B.P. (sp. gr. 0-735). This should stand for 

 at least two days, and should be shaken frequently, or stirred with 

 a glass rod ; when all the gum copal is dissolved, it should form a 

 clear, thin, transparent liquid, and is then ready for immediate use. 



The substance to be hardened should be first well dried in a 

 porcelain dish, upon a hot iron plate placed upon a tripod stand over 



* Amer. Journ. Micr., ii. (1877) pp. 154-5. 



t Proc. B. Phys. Soc. Edin., viii. (1885) pp. 295-BOO (1 pi.). 



