35 
depolarisation of light, 0 c. 
13. Adipocire from muscidar fibre. This substance melts as 
easily as white wax. It depolarises light in every position, 
and crystallizes differently from wax, manna, and sper- 
maceti. 
14. Adipocire from the burying ground of the church des Inno- 
cens at Paris. This substance melts at as low a temperature 
as the preceding, and when cooled between two plates of 
glass, it crystallizes in concentric rings which appear through 
the microscope like clusters of islands in a map, surrounded 
with engraved circles. It has no neutral axes, but depolarises 
light in every position. 
15. Adipocire from biliary calculi. This body crystallizes 
exactly like benzoic acid, which it resembles in appearance, 
shooting out spicula at angles of about so®. It requires a 
very considerable heat to melt it; crystallizes rapidly, and 
depolarises light in every position. 
16. The benzoic and oxalic acids , when melted by heat, and 
then cooled, depolarise light in every position. 
17. Spermaceti. This substance, when melted and cooled, 
depolarises light in every direction ; and when pressed be- 
tween two plates of glass without the aid of heat, it exhibits 
traces of coloured rings by polarised light. 
18. Gold beaters’ shin. Having procured a remarkably thin 
film of this animal substance, I rendered it transparent by 
placing it between layers of Canada balsam. It possessed the 
property of depolarising light, but it did not restore the whole 
of the evanescent pencil. Its neutral axes were not so per- 
fectly developed as in the thin film of caoutchouc. 
19. Transparent and common soap. A plate of transparent 
soap of any thickness depolarises light in every position ; and 
F 2 
