V. 



Continental Growth and Geological Periods. 



IN the early days of Geology a period indicated a certain section 

 of the earth's history distinctly marked off from that which 

 preceded and that which followed. Each period had a fauna and 

 flora peculiar to itself by which it could be recognised through the 

 fossil remains found embedded in its rocks. There is no doubt that 

 the Mosaic account of the Creation gave traditional support to the 

 notion of distinct breaks in the geological chain. Each period repre- 

 sented not unnaturally to early thinkers a separate creation followed 

 by complete destruction. What was first noticed were the salient 

 differences between the fossil contents of strata geologically far apart, 

 such as the reptiles of the Lias and the fishes of the Chalk. Ingenious 

 men found then, as Mr. Gladstone does now, a parallelism in the 

 order of creation between the Mosaic account and the record of the 

 rocks. 



When, however, the record was further searched, interesting links 

 were discovered, which, if they did not actually bridge over the 

 differences, led men to think that, could all be restored, the earth's 

 history would be found to be one continuous record unbroken by cata- 

 clysmic collapses and successive repairs. Curiously enough, these 

 ideas held their ground in face of the uniformitarian theory of the 

 earth given to the world by Hutton at the close of the last century. 

 Lyell, following on the same lines, with a wealth of illustration and 

 rare literary skill, showed that a true interpretation of nature in the 

 past was to be sought in the action of present causes. The science 

 of geology was thus put on a stable base, and men were taught to 

 arrive at their opinions by reasoning upon facts instead of merely 

 giving free scope to their imaginations. The doctrine of uniformity 

 may not be theoretically correct ; indeed, uniformitarianism is a 

 misnomer even as applied to Lyell's conception of the history of the 

 earth. It might with quite as much justice be called development. 

 The popular conception, however, of uniformity was that things are 

 now as they have been in the past and as they will be in the future. 

 From this it resulted that " periods " came to be looked upon only 

 as arbitrary divisions of geological history which enabled one to 

 grasp the sequence of geological events. Indeed, it is but fair to 

 say that there is not in the whole of Lyell's " Principles," for which no 



