OST 



OST 



the other metal was IRIDIUM, which see. 

 The osmium was obtained by heating the 

 black powder with pure alkali in a silver 

 crucible. The oxide of this metal com- 

 bines with the alkali, may be expelled by 

 an acid, and being very volatile, may be 

 obtained by distillation. It does not red- 

 den vegetable blues, but stains the skin of 

 a deep red or black. The oxide, in so- 

 lution with water, has no colour ; but by 

 combining with alkali or lime, it becomes 

 yellow. With the infusion of nut-galls, 

 it gives a very vivid blue colour. It is 

 precipitated by all the metals, excepting 

 gold and platina. An amalgam may be 

 formed with mercury, by agitating it with 

 the aqueous solution of this oxide. When 

 this amalgam is heated, the mercury is 

 driven off, and the pure metal remains 

 behind in the state of black powder. 

 This metal was called osmium on account 

 of the strong smell of the oxide. 



OSMUNDA, in botany, a genus of the 

 Cryptogamiu Filices class and order. Na- 

 tural order of Filices or Ferns. Generic 

 character ; capsules distinct, disposed in 

 a raceme, in such a manner as to look the 

 same way, or else heaped on the back of 

 the pinna or division of the frond, sessile, 

 sub-globular, opening transversely, with- 

 out any ring : seeds very many, extreme- 

 ly minute. There are twenty-seven spe- 

 cies. 



OSSIFICATION, the formation of 

 bones, but more particularly the conver- 

 sion of parts naturally soft to the hardness 

 and consistence of bones. All concre- 

 tions which make their appearance in the 

 solids of the animal body may be compre- 

 hended under this title with propriety, 

 because they have a close resemblance to, 

 and are composed of similar constituents 

 with BOME, which see. In the pineal 

 gland concretions have been found, which 

 consist of phosphate of lime. The same 

 is true of concretions found in the saliva- 

 ry glands, in the prostate, and in the li- 

 ver ; and also in pulmonary concretions. 

 The latter however are found to contain 

 phosphate and carbonate of lime, and in 

 some cases no phosphate, but 



Carbonate of lime 82 



. Animal matter and water 18 



100 



OSTEOLOGY, that branch of anatomy 

 which treats of the bones. 



OSTEOSPERMUM, in botany, a genus 

 of the Syngenesia Polygamia Necessaria 

 class and order. Natural order of Com- 



posite Discoidex. Corymbiferae Jussiei*, 

 Essential character : calyx simple, or in 

 two rows, many -leaved, almost equal ; 

 seeds globular, coloured, bony ; down 

 none ; receptacle naked. There are se- 

 venteen species 



OSTRACION, the trunk fish, in natural 

 history, a genus of fishes, of the order 

 Cartilaginei. Generic character: teeth 

 cylindric, pointing forwards and rather 

 blunt ; body mailed by a complete long 

 covering. There are twelve species. 

 We shall notice only the O. triqueter, or 

 the triangular trunk fish, is about twelve 

 inches long, arid is completely, except to 

 a very short distance rrom the tail, sur- 

 rounded with a bony covering, divided 

 into hexagonal spaces, and overspread 

 with a diaphanous epidermis, resembling 

 thus the armadillo among quadrupeds. It 

 is a native of the American and Indian 

 seas, is thought a high delicacy in India, 

 and lives, it is supposed, on worms and 

 shell fish. 



OSTKEA, the oyster, in natural history, 

 a genus of the Vermes Testacea class and 

 order. Animal a tethys: shell bivalve, 

 generally with unequal'valves and slightly 

 eared ; hinge without teeth, but furnish- 

 ed with an ovate, hollow, and mostly la- 

 teral transverse grooves. About 150 

 species have been enumerated, and class- 

 ed into sections and subsections. A. fur- 

 nished with ears and radiate ; scallop. B. 

 rough, and generally plated on the out- 

 side ; oysters. C. hinge with a perpen- 

 dicular grooved lina. Most of this genus 

 are furnished at the hinge internally with 

 numerous parallel transverse grooves in 

 each valve, and are immediately distin- 

 guished from the genus area, in not hav- 

 ing teeth alternately locked in each other. 

 Scallops leap out of the water to the dis- 

 tance of half a yard, and opening the 

 shells, eject the water within them ; after 

 which they sink under the water, and 

 suddenly close the shells with a loud snap. 

 O. maxima : shell with about fourteen 

 rounded and longitudinally striate rays ; 

 is found in most European seas, in large 

 beds, whence they are dredged up, and 

 pickled and barrelled for sule. This, we 

 are told, is the shell which was formerly 

 worn by pilgrims on the hat or coat, as a 

 mark that they had crossed the sea, for 

 the purpose of pa) ing their devotions at 

 the Holy Land ; in commemoration of 

 which it is still preserved in the arms of 

 many families. O. edulis : shell nearly 

 orbicular and rugged, with undulate im- 

 bricate scales ; one valve flat and very en- 

 tire. Of this species there are many va- 



