GLOSSARY 
OP SOME 
GEOLOGICAL TERMS, 
CHIEFLY FROM MATHEr's GEOLOGY, 
A. 
AlluviaL The adjective of Alluvium. 
Alluvion. A synonyme of Alluvium, 
Alluvium. Recent deposites of earth, sand, gravel, mud, stones, 
peat, shell banks, shell marl, drift sand, &c., resulting from 
causes now in action. This term is generally applied to those 
deposites in v^hich water is the principal agent. 
Alum rocks. Rocks which, by decomposition, form Alum. 
Amorphous. Bodies devoid of regular form. 
Amygdaloid. A trap rock which is porous and spongy, with 
rounded cavities scattered through its mass. Agates and simple 
minerals are often contained in these cavities. 
Anthracite. A species of mineral coal, hard, shining, black, 
and devoid of bitumen. 
Anticlinal. An anticlinal ridge or axis is where the strata 
along a line dip contrariwise, like the sides of the roof of a house. 
Arenaceous. Sandy. 
Argillaceous. Clayey. 
Augite. A simple mineral of variable colour, from black 
through green and gray to white. It is a constituent of many 
volcanic and trappean rocks, and is also found in some of the 
granitic rocks. 
Avalanche. This term is usually applied to masses of ice and 
snow which have slidden from the summits or sides of mountains. 
It is now also applied to shdes of earth and clay. 
B. 
Basalt. One of the common trap rocks. It is composed of 
augite and feldspar, is hard, compact, and dark green or blsick, 
