VOL 



[458] 



WAR 



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

 roll.) A genus of globular animal- 

 cules. To the presence of one 

 species of volvox, the volvox glo- 

 bator, a loricated animalcule, and 

 to its great abundance in such situ- 

 ations, pools of stagnant water owe 

 their green colour. 



YI/LCANIST. One who supports the 

 Vulcanian theory, namely, that all 

 rocks are of igneous production. 

 The Yulcanists were opposed to the 



Neptunians, who, on the other 

 hand, maintained that all rocks 

 were of aqueous origin. 



YUL'CANIAN THE'OEY. That theory 

 which explained the formation of 

 all rocks by the agency of fire. 



YTJ'LPINITE. A mineral of a greyish- 

 white colour; thus named from its 

 being found at Vulpino, in Italy. 



YULVA. (Lat.) In conchology, a 

 spatulated mark in shells of the 

 Yenus tribe. 



W 



WACKE. | A name given by the Ger- 

 WACKE'. ) mans 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 black- 

 ish 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 con- 

 choidal. 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 

 amygdaloid. It is found more 

 abundantly in Germany than any 

 other country, but it is not confined 

 to Germany. 



j Another name for black- 



WADD. ) lead. 



WADD BLACK. A name given to the 

 earthy manganese of Devonshire: 

 it is a hydrate of manganese, and 

 has the peculiar property of taking 

 fire when dry, moderately heated, 

 and mixed with linseed oil. 



WAEM-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 cir- 

 culation is two-fold, there being, in 

 fact, two hearts, perfectly distinct, 

 and separated by thick partitions, 

 which do not permit any direct 

 transmission of fluid from one to 

 the other. These two hearts are 

 joined together, and enclosed with- 

 in one capsule or envelope. The 

 following is the course of circula- 

 tion in warm-blooded animals. 

 From the left ventricle the blood 

 is propelled into the aorta, the great 

 artery of the body, to be by it for- 

 warded into all the arterial ramifi- 



