Page:Collier's New Encyclopedia v. 10.djvu/66

LEFT TUBRET 48 TURTLE blue, bluish-green, apple-green; streak, white; rarely sub-translucent, mostly opaque. Composition: Phosphoric acid, 32.6; alumina, 46.9; water, 20.5=100, whence the formula, 2AI2O3PO0 + 5HO. Probably the Callais, Callaina, and Callaica of Pliny. A gem stone much used in ancient times in Persia, and in prehistoric times by the ancient Mexi- cans under the name of chalchihuitl. Originally found in Persia, where the best stones for jewelry purposes are still obtained, through the locality of the Mexican chalchihuitl has lately been dis- covered. TURRET, in architecture, a small tower attached to and forming part of another tower, or placed at the angles of a church or public building especially in the style of Tudor architecture. Tur- rets are of two kinds — such as rise im- mediately from the ground, as stair- ease turrets, and such as are formed in the upper part of a building by being carried up higher than the rest, as bar- tizan turrets. In military antiquities, a movable building of a square form, con- sisting of 10 or even 20 stories, and sometimes 180 feet high, usually moved on wheels, and employed in approaches to a fortified place for carrying soldiers, engines, ladders, etc. In railways, the elevated central portion of a passenger car, whose top forms an upper story of the roof, and whose sides are glazed for light and pierced for ventilation. TURTLE, in zoology, the pojpular name for any species of the Chelomidse. They may be distinguished by their long, com- pressed fin-shaped, non-retractile feet, with the toes inclosed in a common skin, from which only one or two claws pro- ject. The carapace is broad and much depressed so that when these animals are on shore, and are turned over on their backs, they cannot regain the nat- ural position. Large interspaces be- tween the extremities of the ribs, and retracted within the shell; it is covered above with symmetrical horny shields, and the jaws are armed with sharp, horny sheaths. Turtles are marine HAWK'S-BILL TURTLE LONG-NECKED TURTLE animals; their pinnate feet and light shell render them excellent swimmers. They sometimes live at a great distance from land, to which they periodically re- turn to deposit their soft-shelled eggs (from 100 to 250 in number) in the sand. They are found in all the inter-tropical seas, and sometimes travel into the tem- portions of the sternum always remain cartilaginous, so that the carapace is far lighter than in the tortoises. The head is large and globose, and cannot be SKELETON OF TURTLE perate zones. The flesh and eggs of all the species are edible, though the Indian turtles are less valuable in this respect than those of the Atlantic. The most highly valued of the family is the green turtle {Chelonia viridis), from which turtle soup is made. It attains a large size, sometimes from six to seven feet