Page:Various Forces of Matter.djvu/189

Rh be mixed with a little weak gum water, and then spread over the paper, which must be dried without heat.

Biniodide of mercury is said to be dimorphous; that is, is able to assume two different forms.

($10$) Page 45. "Prince Rupert's Drops." These are made by pouring drops of melted green glass into cold water. They were not, as is commonly supposed, invented by Prince Rupert, but were first brought to England by him in 1660. They excited a great deal of curiosity, and were considered "a kind of miracle in nature."

($11$) Page 46. Thick glass vessels. They are called Proofs or Bologna phials.

($12$) Page 47. Mica. A silicate of alumina and magnesia. It has a bright metallic lustre, hence its name, from mico, to shine.

($13$) Page 48. Common salt or chloride of sodium crystallises in the form of solid cubes, which aggregated together, form a mass, which may be broken up into the separate cubes.

($14$) Page 49. Iceland or calc spar. Native carbonate of lime in its primitive crystalline form.

LECTURE III. ($15$) Page 65. Solution of a salt. Acetate of soda. A solution saturated, or nearly so, at the boiling point, is necessary, and it must be allowed to cool, and remain at rest until the experiment is made.

($16$) Page 71. Binoxide of nitrogen and hyponitrous acid. Binoxide of nitrogen is formed when nitric acid and a little water are added to some copper turnings,