UNIFORMITY OF CHANGE 439 



of an exact science; the greater number of phenomena must 

 for ever remain inexplicable, or only be partially elucidated 

 by ingenious conjectures. Even the mystery which invested 

 the subject was said to constitute one of its principal charms, 

 affording, as it did, full scope to the fancy to indulge in a 

 boundless field of speculation. 



The course directly opposed to this method of philoso- 

 phising consists in an earnest and patient enquiry, how far 

 geological appearances are reconcilable with the effect of 

 changes now in progress, or which may be in progress in 

 regions inaccessible to us, but of which the reality is attested 

 by volcanos and subterranean movements. It also endea- 

 vours to estimate the aggregate result of ordinary operations 

 multiplied by time, and cherishes a sanguine hope that the 

 resources to be derived from observation and experiment, or 

 from the study of Nature such as she now is, are very 

 far from being exhausted. For this reason all theories are 

 rejected which involve the assumption of sudden and vio- 

 lent catastrophes and revolutions of the whole earth, and 

 its inhabitants theories which are restrained by no refer- 

 ence to existing analogies, and in which a desire is mani- 

 fested to cut, rather than patiently to untie, the Gordian 

 knot. 



We have now, at least, the advantage of knowing, from 

 experience, that an opposite method has always put geolo- 

 gists on the road that leads to truth suggesting views which, 

 although imperfect at first, have been found capable of im- 

 provement, until at last adopted by universal consent; while 

 the method of speculating on a former distinct state of things 

 and causes has led invariably to a multitude of contra- 

 dictory systems, which have been overthrown one after 

 the other have been found incapable of modification- 

 and which have often required to be precisely reversed. 



The remainder of this work will be devoted to an investi- 

 gation of the changes now going on in the crust of the earth 

 and its inhabitants. The importance which the student will 

 attach to such researches will mainly depend on the de- 

 gree of confidence which he feels in the principles above 

 expounded. If he firmly believes in the resemblance or 

 identity of the ancient and present system of terrestrial 



