CarruTHEers.—Retardation of Earth’s Rotation by Voleanie Action. 867 
When the strain caused by the tendency to elongation became as great 
as the strength of the crust would bear, the crust would begin to yield, and 
as point after point of it gave way, lofty ranges of mountains would arise 
in every part of the world. The sea would be confined to deep and narrow 
valleys; on every range great glaciers would form; icebergs would be 
floated from the polar seas in immense numbers, and the earth would pass 
through a glacial period. 
When the axis has reached its full length, and the crust was in equili- 
brium, elevation would cease—subsidence, which is never ceasing, would 
still be at work; the mountains would sink into the sea; glaciers would 
disappear, and a period of mild and insular climate would follow, such as 
seems to have characterised the deposition of the Coal Measures. 
If we take 10,000,000 years as the length of this cycle, it would indicate 
180 feet as the amount of elongation of the polar axis, the tendency to which 
would cause fracture of the crust. The elongation due to the tides is two 
feet, so that they should influence to an appreciable extent the times when 
eruptions would take place.* 
* Instead of a short period of 10,000,000 years, the cycle may, perhaps, embrace the 
whole time covered by the geological record, and as far as negative evidence is of value 
the teaching of geology seems favourable to such a supposition. In the oldest formations 
marine fossils only, have hitherto been found, a few land fossils afterwards appear; they 
gradually increase in numbers, as compared with the others, until the land and lacustrine 
flora and fauna assume eventually an importance equal that of the marine. In the 
earlier formations the types of life which predominate in our Museums are such as prefer 
an insular climate; types suited to a rigorous continental climate gradually supplant 
these, and appear to have reached and passed the time of their maximum importance. 
All this may be due to the incompleteness of the record; but it is exactly what would 
follow from the supposition under discussion. Many former geological cycles may have 
existed, each cut off from its oer nee and the last of them cut off from the present 
cycle by a long period, during which t. ole globe was covered by anearly shoreless ocean. 
In each cycle there would have ay continents and mountains as at present, due to 
the elongation of the polar axis, and at the close of each, when the crust had yielded 
completely to ae a to which it was subjected, a long period of subsidence would 
follow, during which the differences between the actual length of the polar axis and the 
length which it a to assume, was too small to cause fracture of the crust. Gradually 
the land would disappear, and with it the whole of the terrestrial flora and fauna, except, 
perhaps, a few genera, which might be preserved on islands. When by the continued 
retardation of the earth’s rotation, the theoretical length of the axis became greatly 
different from the actual, fracture of the crust would again take place, and the land would 
reappear. All fossils of the former cycles would be destroyed by old age. Those of the 
intermediate oceanic period and of the earlier stages of the new cycle, if they lasted long 
enough for us to see, — as the oldest fossils really are, be little more than indica- 
tions of organic matte The genera which had not been destroyed during the oceanic 
riod would, however, — over the newly formed land, and our earliest terrestrial 
fossils would be those of plants and animals with fully specilised organs, so that we 
should have no record of the evolution of the higher forms of life from the lowest. 
