78 
GLOSSARY. 
H, p. 391.), found chiefly in England, in the Island of Portland 
on the coast of Dorsetshire. The great supply of the building 
stone used in London is from these quarries. 
Pozzuolana. Volcanic ashes, largely used as mortar for buildings, 
similar in nature to what is called in this country Roman cement. 
It gets its name from Pozzuoli, a town in the bay of Naples, 
from which it is shipped in large quantities to all parts of the 
Mediterranean. 
Products. An extinct genua of fossil bivalve shells, occurring only 
in the older of the secondary rocks. It is closely allied to the 
living genus Terebratula. 
Pubescence. The soft hairy clown on insects. Etym., pubesco, 
the first growth of the beard. 
Pumice. — A light spongy lava, of a white colour, produced by gases, 
or watery vapour getting access to the particular kind of glassy 
lava called obsidian, when in a state of fusion — it maybe called 
the froth of melted volcanic glass. The word comes from the 
Latin name of the stone, pumex. 
Purbeck Limestone, PurbeckBeds. Limestone strata belonging 
to the Wealden group. See Table II. G, p. 390, 
Pyrites (Iron). A compound of sulphur and iron, found usually in 
yellow shining crystals like brass, and in almost every rock 
stratified and unstratified. The shining metallic bodies, so often 
seen in common roofing slate, are a familiar example of the 
mineral. The word is Greek, and comes from irvp, pyr, fire, 
because, under particular circumstances, the stone produces 
spontaneous heat and even inflammation. 
Quadrumana. The order of mammiferous animals to which apes 
belong. Etym., quadrus, a derivation of the Latin word for 
the number four, and mantis, hand, — the four feet of those 
animals being in some degree usable as hands. 
Qua-qua-versal Dip. The dip of beds to all points of the com- 
pass around a centre, as in the case of beds of lava round 
the crater of a volcano. Etym., qua-qua versum, on every 
side. 
Quartz. A German provincial term, universally adopted in scientific 
language, for a simple mineral composed of pure silex, or earth 
of flints ; rock-crystal is an example. 
Red Marl, A term often applied to the New Red Sandstone, which 
