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WAT 



wreaths or turnings of the shells of uni- 

 valves are termed volutions. 



VO'LVOX. (volvox, Lat. from volvo, to 

 roll. ) A genus of globular animalcules. 

 To the presence of one species of volvox, 

 the volvox globator, a loricated animalcule, 

 and to its great abundance in such situ- 

 ations, pools of stagnant water owe their 

 green colour. 



VU'LCANIST. One who supports the Vulca- 

 nian theory, namely, that all rocks are of 

 igneous production. The Vulcanists were 



opposed to the Neptunians, who, on the 



other hand, maintained that all rocks 



were of aqueous origin. 

 VU'LCANIAN THE'ORY. That theory which 



explained the formation of all rocks by 



the agency of fire. 

 VU'LPINITE. A mineral of a greyish-white 



colour; thus named from its beingfound 



at Vulpino in Italy. 

 VULVA. (Lat.) In conchology, a spatu- 



lated mark in shells of the Venus tribe. 



W 



WACKE. ) A name given by the Germans 

 WACKE'. $ to a soft earthy basalt, to 

 which it is nearly allied, and of which it 

 may be deemed a variety. Its colours are 

 greenish grey, sometimes passing into 

 blackish green, brown, and greyish black, 

 with sometimes a shade of yellow or red. 

 It is invariably opaque. It occurs in 

 amorphous masses, compact or vesicular. 

 Fracture uneven, or slightly conchoidal. 

 Hardness moderate. It is easily broken, 

 and may be cut by a knife. Specific 

 gravity from 2'5 to 2-8. Before the blow- 

 pipe it fuses into an opaque, porous 

 mass. It appears to be intermediate be- 

 tween clay and basalt, often passing into 

 basalt. It does not adhere to the tongue, 

 which circumstance distinguishes it from 

 clay, nor will it form a paste with water. 

 It does not, as does marl, effervesce with 

 acids. Wacke is included among the 

 trap rocks. When wacke, being vesicular, 

 contains within* its cavities calcedony, 

 agates, &c. it forms a variety of amygda- 

 loid. It is found more abundantly in 

 Germany than in any other country, but 

 it is not confined to Germany. 

 WAD. } Another name for plumbago, or 

 WADD. $ black-lead. See Black Lead. 

 WADD BLACK. An ore of manganese. A 

 name given to the earthy manganese of 

 Devonshire : it is a hydrate of manga- 

 nese, and has the peculiar property of 

 taking fire when dry, moderately heated, 

 and mixed with linseed oil. 

 WARM-BLOODED ANIMALS. In the as- 

 cending series of the four great divisions 

 of the animal kingdom, the highest, or 

 vertebrata, alone contains what are called 

 warm-blooded animals. Of this division, 

 consisting of five classes, two classes only, 

 namely aves, or birds, and mammalia, are 

 warm-blooded ; the remaining three are 

 cold-blooded. In warm-blooded animals 

 the circulation is two-fold, there being, 

 in fact, two hearts, perfectly distinct from 

 one another, and separated by thick par- 

 titions, which do not permit any direct 



transmission of fluid from one to the 

 other. These two hearts are joined toge- 

 ther, and enclosed within one capsule or 

 envelope. The following is the course of 

 circulation in warm - blooded animals. 

 From the left ventricle the blood is pro- 

 pelled into the aorta, the great artery of 

 the body, to be by it forwarded into all 

 the arterial ramifications of the whole 

 system ; from these arteries it passes on 

 through the veins into the vense cavse, 

 and by them is carried into the right 

 auricle ; from the right auricle it passes 

 into the right ventricle, and by the right 

 ventricle is propelled into the pulmonary 

 arteries, to be conveyed through the 

 lungs, in its passage through which it 

 becomes aerated, loses its dark and as- 

 sumes a florid colour, and is once more 

 arterial blood ; it then passes into the 

 pulmonary veins, and is conveyed into the 

 left auricle, whence it is forced into the left 

 ventricle, and once more into the aorta. 



WART. A hard excrescence ; a protu- 

 berance. 



WA'RTY. In botany, a term applied to the 

 stems of trees when covered, or studded, 

 with knobs or excrescences. 



WA'TER. (wasser, Germ.) When pure, 

 water is transparent, and destitute of 

 colour, taste, and smell. The specific 

 gravity of water is always supposed = 

 1*000, and it is made the measure of the 

 specific gravity of all other bodies. When 

 water is cooled down to 32 Fah. it as- 

 sumes the form of ice. When heated to 

 the temperature of 212 Fah. it boils, and 

 is converted into steam. Pure water con- 

 sists of two parts of hydrogen and one of 

 oxygen. 



WA'TER OF CRYSTALLIZA'TION. A variety 

 of substances in crystallizing, combine 

 chemically with a certain portion of 

 water, which in a dry state forms an es- 

 sential part of their crystals, and seems, 

 in some cases, to give the peculiar deter- 

 mination to their constituent molecules. 

 Mrs. Somerville. 



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