464 Climate of the Glacial Period. (October, 
occasioned by the slow recovery from the last disturbance 
of that equilibrium. Viewed in these lights, the history of 
the Glacial period has yet to be written; and whoever has 
time and ability to take up the study will find it one of ex- 
treme interest. 
In treating the subject as I have done I know I must 
with many have weakened my argument by introducing 
questions not directly bearing on it. They will turn to 
some text-book and find it stated that the greater part of 
England was submerged 2000 feet below the sea in Glacial 
times; or that the secular cooling of the earth is an in- 
contestable physical necessity; or that in some other way 
I have propounded a scientific heresy. ‘They will fail to see 
that the main argument is not affected by these auxiliary 
theories, and they will decide against me. The human mind 
falls back on precedent and authority, and an original investi- 
gator must expect that every step he takes will be disputed. 
And in many ways the result is most beneficial, for the 
theories that survive do so because they have an innate 
vitality that carries them through all opposition; and those 
that cannot stand the test soon succumb to the chilling 
blasts of gusty criticism. 
There are others, however, who will consider the argument 
strengthened and not weakened by these subsidiary specula- 
tions, for they know that it is characteristic of a true theory, 
like that of gravitation or the undulatory theory of light, 
that it explains numerous facts not originally contemplated 
when it was first suggested. Many must have been led to 
adopt the beautiful theory of the origin of species by natural 
selection, through finding that it afforded welcome help in 
the solution of problems in natural history besides those 
that Darwin first sought to explain by it. And I claim for 
this theory that it shows these signs of truthfulness. It not 
only explains the grand facts of glaciation and of the 
Arctic Tertiary flora, but it throws unexpected light on 
such far removed and seemingly unconnected facts as the 
traditions of a great deluge, the production of volcanic 
eruptions, and the growth of coral islands. It is the 
problem of human knowledge to bring the accumulating 
facts of the world’s history through all time into one con- 
sistent and harmonious chain of consequences, and I trust 
I may in this paper have contributed towards that end. © 
