6 THE PRESIDENTIAL ADDRESS 
rugosities on its surface was a legacy from the nebular hypothesis. 
In spite of the homely simile of a shrivelling apple, this explanation 
has never received a very enthusiastic welcome from geologists, 
though, in default of other resources, they had to make use of it. 
As knowledge has grown the difficulties have become insurmountable 
to them. 
First, there is its inadequacy to explain the vast amount of lateral 
movement required to account for the greater mountain ranges ; 
their rocks, originally spread over a wider area, having been folded 
and crushed into a narrower width. The shortening of the earth- 
crust thus effected has been estimated in the case of the Rocky 
Mountains at 29 miles, of the Himalayas at 62, the Alps at 76, and 
the Appalachians at the large figure of 200 miles. 
Then there is the periodicity of mountain growth. The great 
epochs of mountain-building, such as the Caledonian, to which 
the chief Scottish and Welsh mountains are due, the Hercynian, 
responsible for the Pennine and South Wales, and the Alpine, 
which gave us ‘the wooded, dim, blue goodness of the Weald,’ 
were associated with vast continental development ; and each was 
separated from the next by a period of relative inactivity lasting 
dozens of millions of years. 
Further, there is the fact that the vigour of mountain-building, 
of volcanoes, and of other manifestations of unrest, has shown no 
sign of senility or lack of energy. ‘The geologically recent Alpine- 
Himalayan range is as great, as lofty, and as complicated in structure, 
as were any of its precursors. ‘The active volcanoes of Kilauea, 
Krakatao, or St. Pierre, and those recently extinct in Northern 
Ireland and the Scottish Isles, were as violent and efficient as any of 
those of the Palzozoic Era. The earth is ‘a lady of a certain age,’ 
but she has contrived to preserve her youth and energy as well as 
her beauty. 
But it was when Lord Kelvin’s dictum struck from geology its 
grandest conception, time, that it became vital to re-examine the 
position. He had demonstrated that, if the earth had been con- 
tinuously cooling down at its present rate, its surface must have been 
too hot for the existence of life upon it a limited number of million 
years ago. ‘The concept of geological time, indicated by Hutton 
in his famous saying that in this enquiry ‘we find no vestige 
of a beginning—no prospect of an end,’ had been confirmed by 
data accumulated through the painstaking researches of a host of 
competent and devoted observers all over the world. To them, 
familiar with the tremendous changes, organic and inorganic, that 
the earth had passed through since Cambrian time, it was wholly 
impossible to compress the life story of the earth, or the history of 
life upon it, into a paltry 20 or 30 million years. The slow growth 
