6 Improvements in Physical Science 
larizing light. 
[JAN, 
Hence it is obvious that heat produces a crystalline 
texture in glass, and that the sudden cooling preserves that texture. 
2. Dr. Brewster ascertained that the following bodies have the 
property of depolarizing light, and therefore have a texture analogous 
to that of crystals :— 
Gum-arabic. 
Cherry-tree gum. 
Caoutchouc. 
White wax. 
Mixture of resin and white wax. 
Cells of the bee. 
Manna. 
Camphor. 
Balsam of Tolu. 
Withered film at the root of 
Calla Ethiopica. 
Fibres of flax, hemp, and cotton. 
Thin white semi-transparent leaf 
of sea weed. 
Adipocire from muscular fibre. 
Ditto from the Innocents’ burial 
ground, Paris, 
Ditto from biliary calculi. 
Benzoic and oxalic acids. 
Spermaceti. 
Goldbeaters’ leaf. 
‘Transparent and common soap. 
Human hair. 
Bristles of a sow. 
Fibres of silk and wool. 
Silk-worm gut and sheep gut. 
Human cuticle. 
Parchment. 
Horny excrescence on the human 
foot. 
Transparent film at the joints of 
Cartilaginous breast-bone of a 
chicken. 
Transparent cartilage from the 
shoulder of a sheep. 
Transparent edge of the feathers 
of a quill. 
Down of goose and ostrich fea- 
thers. : 
Flat bones of a cod. 
Cylindrical bones of fish. 
Ivory. 
Whalebone. 
Horn. 
Mother-of-pearl. 
Bladder of a cow. 
Human cornea. 
Cornea of a cow. 
Cornea of a fish. 
Glue. 
Hard isinglass. 
Acetate of lead. 
Glass of borax. 
Amber. 
Gum-animé. 
Sulphur. 
Ice. 
Oil of mace. 
Tallow. 
Tortoise-shell. 
Heated glass. 
Rupert’s drops. 
the claws of the common crab. | Semi-transparent extremity of 
Human nail. 
the legs of a crab. 
A quill, and the thin film which | Tubular film from the body of a 
lines the inside of it. 
crab. 
Dr. Brewster found that the following substances have no effect 
in depolarizing light :— 
Gold leaf. 
Some crystals of diamond. 
Common salt. 
Fluor spar. 
Spinell. 
Sal-ammoniac. 
Rochelle salts. 
Nitrate of lead. 
Sclerotic coat of a fish. 
Crystalline lens of a fish. 
Crystalline lens of a cow, 
Capsule of the lens of a fish. 
