309 
1877*] Probable Origin and Age of the Sun . 
It is true that the views which formerly prevailed amongst 
geologists, in regard to the almost unlimited extent of geo- 
logical time, have of late undergone very considerable modi- 
fications ; but there are few geologists, 1 presume, who 
would be willing to admit that the above period is sufficient 
to comprehend the entire history of stratified rocks. 
It is the fadls of denudation which most forcibly impress 
the mind with a sense of immense duration, and show most 
convincingly the great antiquity of the earth. 
We know unquestionably that many of the greatest 
changes undergone by the earth’s crust were produced, not 
by convulsions and cataclysms of nature, but by those or- 
dinary agencies that we see at work every day around us, 
such as rain, snow, frost, ice, chemical adtion, &c. Valleys 
have not been produced by violent dislocations, nor the hills 
by upheavals, but both have been carved out of the solid rock 
by the silent and gentle agency of chemical adbion, frost, rain, 
ice, and running water. In short, the rocky face of our globe 
has been moulded into hill and dale, and ultimately worn 
down to the sea-level by means of these apparently trifling 
agents, not merely once or twice, but probably dozens of times 
over during past ages. Now when we refledt that with such 
extreme slowness do these agents perform their work that we 
might, if we could, watch their operations from year to year, 
and from century to century, without being able to perceive 
that they make any sensible impression, we are necessitated 
to conclude that geological periods must be enormous. 
The utter inadequacy of a period of 20 million years for 
the age of our earth is demonstrable from the enormous 
thickness of rock which is known to have been removed off 
certain areas by denudation. I shall now briefly refer to 
a few of the many fadts which might be adduced on this 
point. 
One plain and obvious method of showing the great 
extent to which the general surface of the country has been 
lowered by denudation is furnished, as is well known, by the 
way in which the inequalities of surface produced by 
faults or dislocations have been effaced. It is quite com- 
mon to meet with faults where the strata on the one 
side have been depressed several hundreds — -and in some 
cases thousands-— of feet below that on the other, but we 
seldom find any indications of such on the surface, the ine- 
qualities on the surface having been all removed by denuda- 
tion. But in order to effedt this a mass of rock must have 
been removed equal in thickness to the extent of the disloca- 
tion. The following are a few examples of large faults 
