Missing Chapters of Geological History. 29 



muds having become shales or schists, limestone silicified, or 

 the thousand other changes having occurred that are familiar 

 to geologists in old rocks; when large sections have been 

 denuded and pared away, and the rest is lifted up so as to 

 incline at a great angle to the horizon, and when finally this 

 upheaved rock has once more become an ocean-floor, the recep- 

 tacle of fresh deposits in which there is no one form of life 

 identical with those of the underlying rocks, we may trace in 

 the break and the unconformability as good evidence of the 

 lapse of time, as if we could count the centuries that have 

 elapsed. 



The gaps in the geology of one country are occasionally 

 filled up in another, and thus we often have independent evi- 

 dence of the lapse of time corresponding to the palgeontological 

 break. Thus, among the older rocks we find large and im- 

 portant series of Devonian rock containing whole groups of 

 characteristic fossils, magnificently developed in Western and 

 Northern Europe, but very imperfectly rendered with us. So 

 also in the Triassic period the fossiliferous strata and even the 

 rocks are altogether so poorly developed in England that for a 

 long time the formation was regarded as subordinate and un- 

 important. And yet in this case the Continental representatives 

 are fully as important as the Oolitic series of the same districts. 

 Similar examples occur in the Neocomian representatives of 

 the lower Grreensand and the Miocene or middle Tertiary 

 series. Indeed, when we approach recent times the accumula- 

 tions of material in one country filling up what are apparently 

 unimportant gaps in another, are so large and important as to 

 justify us in attributing very long periods of time to very small 

 differences of specific character. 



Let us, with the light we now possess as to the conditions 

 of accumulation and the physical breaks, whether biological or 

 stratigraphical, endeavour to recapitulate very generally the 

 succession of geological events in England. The oldest forma- 

 tions were probably deposited in deep seas during depression, 

 and these deposits once formed were depressed, metamor- 

 phosed, and re-elevated again and again at a time when there 

 was little land in the Northern hemisphere. Towards the 

 middle part of the great Silurian period when the Llandovery 

 rocks were deposited, the sea-bottom had become elevated, and 

 was almost a beach. Then succeeded another period of de- 

 pression. During the Devonian period there was enormous 

 and comparatively rapid denudation — the materials washed 

 away being of course Silurian strata, and in some places accu- 

 mulations of clayey mud and sand were deposited at moderate 

 depths, while elsewhere coarse conglomerates were rapidly 

 heaped together. The older part of the Carboniferous series 



