In this book, geology was, for the first time, declared to be in no way concerned about the origin of things. It was the first in which an attempt was made to dispense entirely with all hypothetical causes, and to explain the former changes of the earth’s crust by reference exclusively to such natural agents as still exist. Hutton laboured to give fixed principles to geology, as Newton had succeeded in doing to astronomy. He wrote: “The ruins of an older world are visible in the present structure of our planet, and the strata which now compose our continents, have been once beneath the sea, and were formed out of the waste of pre-existing continents. The same forces are still destroying, by chemical decomposition or mechanical violence, even the hardest rocks, transporting the materials to the sea, where they are spread out and form strata analogous to those of more ancient date. Although loosely deposited along the bottom of the ocean, they become afterwards altered and consolidated by volcanic heat, and then turned up, fractured, and contorted.” He showed that many hard crystalline rocks, such as basalt, were of igneous origin, and that some of them had been injected in a melted state through fissures in the older strata. He proved, by examining Glen Tilt, that granite was once in a state of fusion, and had cooled. He wrote: “In the economy of the world I can find no traces of a beginning, no prospect of an end,” a declaration all the more startling when coupled with the doctrine that all changes on the globe had been brought about by the slow agency of existing causes. Sir Charles Lyell, writing on this, stated, “The imagination was first fatigued and overpowered by endeavouring to conceive the immensity of time required for the annihilation of whole continents by so insensible a process; and when the thoughts had wandered through these intermediate periods, no resting place was assigned in the remotest distance. The oldest rocks were represented to be of a derivative nature, the last of an antecedent series, and that, perhaps, of one of many pre-existing worlds.”