130 D. E. GODDARD ON MANIPULATION WITH CANADA BALSAM. 



jar, containing a smaller one partly filled with the strong acid. 

 Chloride of calcium would answer the same purpose . 



The object is placed on a slip of glass over the vessel containing 

 the drying agent, and the whole rendered comparatively air tight 

 by a disc of glass, with greased edges placed on the top of the 

 large jar. This plan I think most generally useful. 



To remove grease or fatty matter, I generally employ benzole. 

 Unless this precaution is taken, and, say fish scales, are mounted, 

 the preparation will probably be a failure. 



To illustrate the methods of drying with alcohol and the acid 

 bath, I will give an example of each. 



Suppose a section of wood is required. I take a twig of any 

 bough — say hazel ; having cut my section, I place it in strong 

 alcohol, where it remains for at least one week ; it is then trans- 

 ferred to camphine, in both processes it is submitted to the air pump. 



Again, I have injected a kidney with gelatine and carmine ; with 

 a valentins knife I cut the section, and as heat could not be ap- 

 plied without liquifying the gelatine, I place it in a vessel such as 

 I have described. In a few weeks it is sufficiently dry to mount ; 

 all the moisture having been absorbed by the sulphurie acid or the 

 chloride of calcium. 



We now come to the final cleaning and finishing. Nothing is 

 more deceptive than the apparent state of the balsam. Often have 

 I finished a number of slides that I imagined were sufficiently set, 

 and in the course of a few weeks the object has entirely disappeared 

 in the rim of varnish. 



To ascertain whether the balsam is sufficiently set, I try it with 

 my nail ; if any indentation is produced, I repeat the hardening 

 process, until, when cold, the nail only scratches. 



The superfluous balsam may then easily be chipped off with a 

 knife. It is possible to clean slides at an earlier period. First 

 remove the excess of balsam with a warm knife, then brush briskly 

 with a soft tooth brush, dipped in mythelated spirit, and finally 

 wipe with a clean white handkerchief. 



The size and nature of the object, and also its destination, must 

 decide the operator which of these methods will be most advisable. 

 With large objects such as wood sections, algas, &c, the balsam 

 need not be so thoroughly hard as when the slide consists of small 

 dense particles, such as diatoms, foraminifera, sponge, spicules, 

 sections of hairs, &c. 



