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however, when compared with the other more valuable part of the fish is an object of little attention to the whale fishers (65). The principal uses to which whalebones are now applied are spokes to wheels of light carriages, fishing rods, whips, sticks, &c.
Ores of Zinc form two distinct substances, as Blende or Black Jack, and Calamine; both of which present several varieties, though they form the same metal. Blende is commonly black, brown, or yellow, of different shades; it is massive, and often appears in clusters upon the surface of other minerals; it may be easily cut by the knife, and by scratching it, a lighter coloured powder is produced; some of the yellow varieties, when rubbed even with a pen, yield phosphorescent sparks. These ores resemble tin, but are neither so heavy nor so hard. Common Calamine greatly resembles some of the earthy minerals; it is frequently cellular, not unlike bone; but its weight will lead to a detection of its me. tallic nature; it strongly effervesces with acids, and occurs in masses, brown, yellow, and green. It is found in great abundance in Derbyshire, and other limestone couuties. Qres of Zinc are of recent dis
covery in this country, the metal being formerly imported from China. A new metal, called Cadmium, bas lately been discovered in the Derbyshire Calamine. Besides the use of Zinc in medicine, it is of great importance in the arts. Mixed with copper in different proportions, it forms brass and pinchbeck; and united with tin, it forms a kind of pewter. From its inflammable properties it is sometimes used in fire-works. The Sulphate of Zinc forms white vitriol (66).
(1) Essential Oils are obtained only from
substances; which oil being collected, the fragrance of the flower from which it is extracted, so fugitive in the common course of nature, is preserved, and, as it were, embodied and made permanent. Essential oils of vegetables are prepared by distillation. They contain the fragrance, warmth, and frequently the active powers of the substance from which they are drawn; whence they have received the name of Essences or Essential Oils. To the former kind, belong the oils of roses, camomiles, &c.; to the latter, the oils of cloves, &c.
(2) Distillation is the art of separating or drawing off
the spiritous, watery, oily, or saline particles of a mashed body from the grosser and more earthy parts by the aid of fire, and then collecting and condensing them by the application of cold.
(3) Alkali is a term given to substances which excite fermentation when united with acids.
It was originally applied only to the salt extracted from the ashes of the plant Kali. Alkaline substances are of various kinds, but the fixed alkalies are potash and soda, and there is a volatile alkali, called ammoniac; potash is obtained by burning vegetables; soda from sea salt; and ammoniac from animal substances, and in the distillation of coals for gas. Alkalies have the property of converting vegetable blues into greens, and combined with acids, neutralize each other, and form the neutral salts. Mixed with fats, they make soap; and melted with silex (now called Quartz), glass.
(4) If a salt be dissolved in water, it is said to be in
(5) When vegetable juices, watery or spiritous de.
coctions, or infusions, are exposed to a continual heat, the fluid gradually evaporating carries off with it such volatile matters as it was impregnated with, and leaves the more fixed united together in
The mass which remains from the evaporation of the expressed juice of a plant, is called inspissated juice ; from watery decoctions or infusions, an extract; (which term is also frequently used as a general appellation for all three kinds) and from spiritous tinctures, a resin, or essential extract.