THE EAKLY RECORDS HAVE BEEN DESTROYED. 355 



gists generally admit, the Earth's crust has resulted from 

 that slow cooling which is even still going on — if we see no 

 sign that at the time when the earliest Cambrian strata 

 were formed, this crust was appreciably thinner than now ; 

 we are forced to conclude that the era during which it 

 acquired that great thickness possessed in the Cambrian 

 period, was enormous as compared with the interval be- 

 tween the Cambrian period and our own. But during the 

 incalculable series of epochs thus inferred, there existed an 

 ocean, tides, winds, waves, rain, rivers. The agencies by 

 which the denudation of continents and filling up of seas 

 have all along been carried on, were as active then as now. 

 Endless successions of strata must have been formed. And 

 when we ask — Where are they ? Nature's obvious reply 

 is — ^They have been destroyed by that igneous action to 

 which so great a part of our oldest-known strata owe their 

 fusion or metamorj^hosis. 



Only the last chapter of the Earth's history has come 

 down to us. The many previous chapters, stretching back 

 to a time immeasurably remote, have been burnt ; and 

 with them all the records of life we may presume they con- 

 tained. The greater part of the evidence which might 

 have served to settle the Development-controversy, is for 

 ever lost ; and on neither side can the arguments derived 

 from Geology be conclusive. 



" But how happen there to be such evidences of pro- 

 gression as exist ? " it may be asked. " How happens it 

 that, in ascending from the most ancient strata to the most 

 recent strata, we do find a succession of organic forms, 

 which, however irregularly, carries us from lower to high- 

 er ? " This question seems difficult to answer. Neverthe- 

 less, there is reason for thinking that nothing can be safely 

 inferred from the apparent progression here cited. And 

 the illustration which shows as much, will, we believe, also 

 show how little trust is to be placed in certain geological 



