SEPTEMBER 21, 1899] 
NATURE 
497 
gradually transforming the face of the existing continents. 
When he stood face to face with the proofs of decay among the 
mountains, there seems to have arisen uppermost in his mind the 
thought of the immense succession of ages which these proofs 
revealed to him. His observant eye enabled him to see ‘‘ the 
operations of the surface wasting the solid body of the globe, 
and to read the unmeasurable course of time that must have | 
flowed during those amazing operations, which the vulgar do 
not see, and which the learned seem to see without wonder” 
(‘‘ Theory of the Earth,” vol. i. p. 108). In contemplating the 
stupendous results achieved by such apparently feeble forces, 
Hutton felt that one great objection he had to contend with in 
the reception of his theory, even by the scientific men of his 
day, lay in the inability or unwillingness of the human mind to 
admit such large demands as he made on the past. ‘* What 
more can we require?” he asks in summing up his conclusions ; 
and he answers the question in these memorable words : *‘ What 
more can we require? Nothing but time. It is not any part of 
the process that will be disputed; but after allowing all the 
parts, the whole will be denied ; and for what ?—only because 
we are not disposed to allow that quantity of time which the 
ablution of so much wasted mountain might require” (of. c7v. 
vol. ii. p. 329). 
Far as Hutton could follow the succession of events registered 
in the rocky crust of the globe, he found himself baffled by the 
closing in around him of that dark abysm of time into which 
neither eye nor imagination seemed able to penetrate. He well 
knew that, behind and beyond the ages recorded in the oldest of 
the primitive rocks, there must have stretched a vast earlier 
time, of which no record met his view. He did not attempt 
to speculate beyond the limits of his evidence. ‘‘I do not 
pretend,” he said, ‘‘to describe the beginning of things ; I take 
things such as I find them at present, and from these I reason 
with regard to that which must have been (of. c2¢. vol. i. 
p- 173, 70¢e). In vain could he look, even among the oldest 
formations, for any sign of the infancy of the planet. Hecould 
only detect a repeated series of similar revolutions, the oldest 
of which was assuredly not the first in the terrestrial history, 
and he concluded, as ‘“‘the result of this physical inquiry, that 
we find no vestige of a beginning, no prospect of an end ” (04. 
cit. vol. i. p. 200). 
This conclusion from strictly geological evidence has been 
impugned from the side of physics, and, as further developed 
by Playfair, has been declared to be contradicted by the 
principles of natural philosophy. But if it be considered on the 
basis of the evidence on which it was originally propounded, it 
was absolutely true in Hutton’s time and remains true to-day. 
That able reasoner never claimed that the earth has existed from 
all eternity, or that it will go on existing for ever. He admitted 
that it must have hada beginning, but he had been unable to 
find any vestige of that beginning in the structure of the planet 
itself. And notwithstanding all the multiplied researches of 
the century that has passed since the immortal ‘‘ Theory of the 
Earth” was published, no relic of the first condition of our 
earth has been found. We have speculated niuch, indeed, on 
the subject, and our friends the physicists have speculated still 
more. Some of the speculations do not seem to me more 
philosophical than many of those of the older cosmogonists. As 
far as trustworthy evidence can be drawn from the rocks of the 
globe itself, we do not seem to be nearer the discovery of the 
beginning than Hutton was. The most ancient rocks that can 
be reached are demonstrably not the first-formed of all. They 
were preceded by others which we know must have existed, 
though no vestige of them may remain. 
It may be further asserted that, while it was Hutton who first | 
impressed on modern geology the conviction that for the 
adequate comprehension of the past history of the earth vast | 
periods of time must be admitted to have elapsed, our debt of 
obligation to him is increased by the genius with which he 
linked the passage of these vast periods with the present 
economy of nature. He first realised the influence of time as a 
factor in geological dynamics, and first taught the efficacy of the 
quiet and unobtrusive forces of nature. His predecessors and 
contemporaries were never tired of invoking the more vigorous 
manifestations of terrestrial energy. They saw in the com- 
position of the land and in the structure of mountains and 
valleys memorials of numberless convulsions and cataclysms. 
In Hutton’s philosophy, however, ‘‘it is the little causes, long 
continued, which are considered as bringing about the greatest 
changes of the earth ” (‘‘ Theory of the Earth,’ vol. ii. p. 205). 
NO. 1560, VOL. 60] 
And yet, unlike many of those who derived their inspiration 
from his teaching, but pushed his tenets to extremes which he 
doubtless never anticipated, he did not look upon time as a kind 
of scientific fetich, the invocation of which would endow with 
efficacy even the most trifling phenomena. As if he had fore- 
seen the use that might be made of his doctrine, he uttered this 
remarkable warning : ‘* With regard to the effect of time, though 
the continuance of time may do much in those operations which 
are extremely slow, where no change, to our observation, had 
appeared to take place, yet, where it is not in the nature of 
things to produce the change in question, the unlimited course 
of time would be no more effectual than the moment by which 
we measure events in our observations.” (0f. cé¢. vol. i. p. 44). 
We thus see that in the philosophy of Hutton, out of which 
so much of modern geology has been developed, the vastness of 
the antiquity of the globe was deduced from the structure of the 
terrestrial crust and the slow rate of action of the forces by which 
the surface of the crust is observed to be modified. But no 
attempt was made by him to measure that antiquity by any of 
the chronological standards of human contrivance. He was 
content to realise for himself and to impress upon others that 
the history of the earth could not be understood, save by the 
admission that it occupied prolonged though indeterminate ages 
in its accomplishment. And assuredly no part of his teaching 
has been more amply sustained by the subsequent progress of 
research, 
Playfair, from whose admirable ‘‘Illustrations of the Hut- 
tonian Theory ” most geologists have derived all that they know 
directly of that theory, went a little further than his friend and 
master in dealing with the age of the earth. Not restricting 
himself, as Hutton did, to the testimony of the rocks, which 
showed neither vestige of a beginning nor prospect of an end, 
he calledrin the evidence of the cosmos outside the limits of our 
planet, and declared that in the firmament also no mark could 
be discovered of the commencement or termination of the present 
order, no symptom of infancy or old age, nor any sign by which 
the future or past duration of the universe might be estimated 
(** Illustrations of the Huttonian Theory, § 118). He thus ad- 
vanced beyond the strictly geological basis of reasoning, and 
committed himself to statements which, like some made also 
by Hutton, seem to have been suggested by certain deductions 
ot the French mathematicians of his day regarding the stability 
of the planetary motions. His statements have been disproved 
by modern physics ; distinct evidence, both from the earth and 
the cosmos, has been brought forward of progress from a begin- 
ning which can be conceived, through successive stages to an 
end which can be foreseen. But the disproof leaves Hutton’s 
doctrine about the vastness of geological time exactly where it 
was, Surely it was no abuse of language to speak of periods as 
being vast, which can only be expressed in millions of years. 
It is easy to understand how the Uniformitarian school, which 
sprang from the teaching of Hutton and Playfair, came to believe 
that the whole of eternity was at the disposal of geologists. In 
popular estimation, as the ancient science of astronomy was 
that of infinite distance, so the modern study of geology was 
the science of infinite time. It must be frankly conceded that 
geologists, believing themselves unfettered by any limits to their 
chronology, made ample use of their imagined liberty. Many 
of them, following the lead of Lyell, to whose writings in other 
respects modern geology owes so deep a debt of gratitude, 
became utterly reckless in their demands for time, demands 
which even the requirements of their own science, if they had 
adequately realised them, did not warrant. The older geolo- 
gists had not attempted to express their vast periods in terms of 
years. The indefiniteness of their language fitly denoted the 
absence of any ascertainable limits to the successive ages with 
which they had to deal. And until some evidence should be 
discovered whereby these limits might be fixed and measured 
by human standards, no reproach could justly be brought against 
the geological terminology. It was far more philosophical to 
be content, in the meanwhile, with indeterminate expressions, 
than from data of the weakest or most speculative kind to 
attempt to measure geological periods by a chronology of years 
or centuries. 
In the year 1862 a wholly new light was thrown on the 
question of the age of our globe and the duration of geological 
ume by the remarkable paper on the Secular Cooling of the 
Earth communicated by Lord Kelvin (then Sir William Thomson) 
to the Royal Society of Edinburgh (Zyvans. Roy. Soc. Edin., 
vol, xxili,, 1862). In this memoir he first developed his now 
