The object of this essay is to view the science of Geology on a more extended scale than is generally attempted in popular treatises; not dwelling on matters of detail, but regarding physical principles and fundamental propositions with those logical sequences by which remoter conclusions are arrived at.

“But how, it may be asked, is the student or mere general reader to enter upon these larger views of the subject without a previous acquaintance with its details? And, doubtless, if any one would make himself an accomplished geologist, and prepare himself to enter fully into the more profound investigations of the science, he must gain a knowledge of its phenomena with a certain degree of detail; but the more complete a science becomes as a science of observation, the less necessary is it for the philosopher who would solve its physical problems to become himself an observer. Newton and Laplace troubled themselves little in looking through astronomical telescopes. They took their facts on the authority of others. And so, also, the general geological reader may accept the facts established by the observations of the field-geologist, when he would acquaint himself with the conclusions of those who have endeavoured to solve the physical or palæon-tological problems which the science presents to us.”