Igneous Rocks and their Origin

Abstract

PROF. DALY is a man of ideas. A few facts observed in the field suggest to him a hypothesis which he then proceeds to test by searching for other facts which must exist if the hypothesis be of any value for scientific purposes. He is perhaps most widely known as the author who, more than any other, has developed the theory of “magmatic stoping.” Large masses of plutonic rock—such, for example, as the granites of Devon and Cornwall—can be proved by field evidence to fill spaces that must formerly have been occupied by other rocks. In the case referred to the displaced rocks consisted largely of folded sediments. What has become of them? According to the theory in question, the roof of the magmatic chamber has been shattered, and the detached fragments have in general sunk in the rising plutonic magma. This theory is explained and illustrated in the present volume, and much use is made of one of its probable consequences—namely, the development of secondary magmas by “syntexis”; or, in other words, by the solution in the rising magma of the masses detached from the walls and roof of the magma chamber. This action is believed to account directly or indirectly for many varieties of igneous rock.

Igneous Rocks and their Origin.

By Prof. R. A. Daly. Pp. xxii + 563. (London: Hill Publishing Co., Ltd.; New York: McGraw-Hill Book Co., Inc., 1914.) Price 17s. net.