G Y R
G Y R
GYPSUM (Cycl.) in natural hiftory, the name of aclafs of foflils ; the characters of which are thefc. They are compofed of fmall flat particles, irregularly arranged, and giving the whole mafles fomething of the appearance of the fofter marbles ; they are bright, glofly, and in a fmati degree tranfparent : not flexile nor elaftic, not giving fire with fteel, nor fermenting with or diflbluble in acid menftruums, and calcine very eafily in the fire. Hill's Hift. of Foflils, p. in.
Of this clafs of bodies there are two orders, and under thofe four genera. The firft order is of the gypfums, which are of a firm compact texture, and confiderably hard. The fecond of thofe which are of a lax or loofe texture, and are accordingly foft and crumbly.
The genera of the firft order of the gypfums are thefe. x. Thofe which are hard, compofed of fomewhat broad particles, and of a bright cryftalinc luftre ; the phoUdes. 2. Thofe of a fofter texture, compofed of very fmall parti- cles, and of a lefs glittering hue ; the lepra. Id. Ibid. The genera of the fecond order are, I. Thofe of a fofter texture, which are very bright and glittering ; the tima- chides. 2. Thofe of a fofter texture, which are dull and opake ; the clafmia. All the fpecies of this whole clafs burn with a very flight degree of fire, to what is commonly called plaifter of Paris : but the fofter require the fmaller de- grees of fire ; and, in general, the harder and more marbly make the better plaifter.
The common way of burning this ftone into plaifter, is too flight to give it all the hardnefs it is capable of. It is re- ported by many, that a greater degree of heat renders it greatly fupcrior in hardnefs ; and, it is faid, that the artificial marble, with which the whole palace of Munich is adorn- ed, and which the elector of Bavaria efteems more than marble, for which it is miftaken by all that fee it, is made
of the common gyp/urn, firft burnt hi the ordinary way and afterwards put over the fire again in a copper veflel, and fuffered to boil, as it will like water for a long time. When this boiling ceafes of itfclf, the matter is taken out, and com- mon colours, fuch as are ufed in painting, are mixed with it in various proportions ; which on the wetting it with water and working it in the common manner of plaifter of Paris diffufe themfelves, and imitate the veins of natural marble Phil. Tranf. N° 9 3.
Gypfu?n is ufed in the Canaries by way of remedy for their wine, and about Malaga a large quantity is tunned up with the juice of their grapes. Boyle's Works abr. Vol. i. p. 146.
GYPSY, a name given to a fet of vagrants. See the arti- cle Bohemians.
GYRFALCO, in zoology, the name of a large and fierce fpe- cies of falcon, called in Englifh thejerfalcon. See the arti- cle Falcon.
Its name is a compound of the German gyr which fignifies a vulture, an<\ falco the fa fan. It is the largeft of all the falcon kind, its head is flatted and of a greyifh colour, its beak very thick and ftrong, but more, and of a blueifh co- lour. The iris of its eyes is blue, and its back, wings, belly and tail are white, but raoft of the back and wing feathers are variegated with one black fpot, of a cordated form, and in fome degree refembling the eye fpots in the peacock's tail. The long wing feathers have alfo a large black fpot near their extremities. The throat, breaft, and belly are of a pure white. The tail is fhort, and variegated with tranfverfe black lines. The legs are thick and ftrong, and both they and the feet are of a pale blue. Ra/s Ornithol. p. 44. It is a very bold and daring bird, attacking all other fowl without referve, and particularly the heron and ftork kind*. The other falcons are all afraid of this.
H.
