GLOSSARY. 
83 
Veins, Mineral. Cracks in rocks filled up by substances different 
from tbe rock, wbicb may either be earthy or metallic. Veins 
are sometimes many yards wide ; and they ramify or branch off 
into innumerable smaller parts, often as slender as threads, like 
the veins in an animal, and hence their name, 
Verteb rated Animals. A great division of the animal kingdom, 
including all those which are furnished with a back-bone, as the 
mammalia, birds, reptiles, and fishes. The separate joints of the 
back-bone are called vertebras, from the Latin verb verto, to turn. 
Vesicle. A small circular inclosed space, like a little bladder. 
Etym., diminutive of vesica, Latin for a bladder. 
Volcanic Bombs. Volcanos throw out sometimes detached masses 
of melted lava, which, as they fall, assume rounded forms (like 
bomb-shells), and are often elongated into a pear shape. 
Volcanic Foci. The subterranean centres of action in volcanos, 
where the heat is supposed to be in the highest degree of 
energy. 
Zeolite. A family of simple minerals, including stilbite, meso- 
type, analcime, and some others, usually found in the trap or 
volcanic rocks. Some of the most common varieties swell or 
boil up when exposed to the blow-pipe, and hence the name 
of fyw, zeo, to froth, and \idos, lithos, stone. 
Zoophytes. Corals, sponges, and other aquatic animals allied to 
them, so called because, while they are the habitation of animals, 
they are fixed to the ground, and have the forms of plants. 
Etym., ^wov, zoon, animal, and tyvrov, phyton, plant. 
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