500 
NATURE 
[SEPTEMBER 21, 1899 
mow in the channels of brooks or on the shores of lake and sea. 
‘They have been laid gently down above each other, layer over. 
layer, with fine sand sifted in between them, and this deposition 
has taken place along shores which, though the waters that 
washed them have long since disappeared, can still be followed 
for mile after mile across the mountains and glens of the North- 
west Highlands. So tranquil were these waters that their gentle 
currents and oscillations sufficed to ripple the sandy floor, to 
arrange the sediment in laminz of current-bedding, and to 
separate the grains of sand according to their relative densities. 
We may even now trace the results of these operations in thin 
darker layers and streaks of magnetic iron, zircon, and other 
heavy minerals, which have been sorted out from the lighter 
quartz-grains, as layers of iron-sand may be seen sifted together 
by the tide along the upper margins of many of our sandy 
beaches at the present day. 
In the same ancient formation there occur also various inter- 
calations of fine muddy sediment, so regular in their thin alter- 
mations, and so like those of younger formations, that we cannot 
but hope and expect that they may eventually yield remains of 
organisms which, if found, would be the earliest traces of life 
in Europe. 
It is thus abundantly manifest that even in the most ancient 
of the sedimentary registers of the earth’s history, not only is there 
no evidence of colossal floods, tides and denudation, but there 
is incontrovertible proof of continuous orderly deposition, such 
as may be witnessed to-day in any quarter of the globe. The 
same tale, with endless additional details, is told all through the 
stratified formations down to those which are in the course of 
accumulation at the present day. 
Not less important than the stratigraphical is the palonto- 
logical evidence in favour of the general quietude of the geo- 
logical processes in the past. The conclusions drawn from the 
nature and arrangement of the sediments are corroborated and 
much extended by the structure and manner of entombment of 
the enclosed organic remains. From the time of the very 
earliest fossiliferous formations there is nothing to show that 
either plants or animals have had to contend with physical 
conditions of environment different, on the whole, from those 
in which their successors now live. The oldest trees, so far 
as regards their outer form and internal structure, betoken an 
atmosphere neither more tempestuous nor obviously more im- 
pure than that of to-day. The earliest corals, sponges, crus- 
taceans, molluscs, and arachnids were not more stoutly con- 
structed than those of later times, and are found grouped together 
among the rocks as they lived and died, with no apparent indi- 
cation that any violent commotion of the elements tried their 
strength when living, or swept away their remains when 
dead. 
But, undoubtedly, most impressive of all the paleontological 
data is the testimony borne by the grand succession of organic 
remains among the stratified rocks as to the vast duration of 
time required for their evolution. Prof. Poulton has treated 
this branch of the subject with great fulness and ability. We do 
not know the present average rates of organic variation, but all 
the available evidence goes to indicate their extreme slowness. 
They may conceivably have been more rapid in the past, or they 
may have been liable to fluctuations according to vicissitudes of 
énvironment.' But those who assert that the rate of biological 
evolution ever differed materially from what it may now be in- 
ferred to be, ought surely to bring forward something more than 
mere assertion in their support. In the meantime, the most 
philosophical course is undoubtedly followed by those biologists 
who in this matter rest their belief on their own experience 
among recent and fossil organisms. 
So cogent do these geological and palzontological arguments 
appear, to those at least who have taken the trouble to master 
them, that they are worthy of being employed, not in defence 
merely, but in attack. It seems to me that they may be used 
with effect in assailing the stronghold of speculation and assump- 
tion in which our physical friends have ensconced themselves 
and from which, with their feet, as they believe, planted well 
within the interior of the globe and their heads in the heart of 
the sun, they view with complete unconcern the efforts made 
by those who endeavour to gather the truth from the surface 
and crust of the earth. That portion of the records of ter- 
! See an interesting and suggestive paper by Prof. Le Conte on 
al Periods in the History of the Earth,” Bxdl. Deft. Geology, 
Uy ity of California, vol. 1. (1895), p. 3133; also one by Prof. Cham- 
berlin on ‘* The Ulterior Basis of Time-divisions and the Classification of 
Geological History,” Journal of Geology, vol. vi. (1898), p. 449. 
NO. 1560, VOL. 60] 
restrial history which lies open to our investigation has been 
diligently studied in all parts of the world. A vast body of 
facts has been gathered together from this extended and com- 
bined research. The chronicle registered in the earth’s crust, 
though not complete, is legible and consistent. From the latest 
to the earliest of its chapters the story is capable of clear and 
harmonious interpretation by a comparison of its pages with the 
present condition of things. We know infinitely more of the 
history of this earth than we’ do of the history of the sun. 
Are we then to be told that this knowledge, so patiently ac- 
cumulated from-innumerable observations and so laboriously 
coordinated and classified, is to be held of none account in 
comparison with the conclusions of physical science in regard 
to the history of the central luminary of our system? These 
conclusions are founded on assumptions which may or may not 
correspond with the truth. They have already undergone 
revisicn, and they may be still further modified as our 
slender knowledge of the sun, and of the details of its 
history, is increased by future investigation. In the meantime, 
we decline to accept them as a final pronouncement of science 
on the subject. We place over against them the evidence 
of geology and paleontology, and affirm that unless the de- 
ductions we draw from that evidence can be disproved, we are 
entitled to maintain them as entirely borne out by the testimony 
of the rocks. 
Until, therefore, it can be shown that geologists and palzeon- 
tologists have misinterpreted their records, they are surely well 
within their logical rights in claiming as much time for the 
history of this earth as the vast body of evidence accumulated by 
them demands. So far as I have been able to form an opinion, 
one hundred millions of years would suffice for that portion of 
the history which is registered in the stratified rocks of the crust. 
But if the paleontologists find such a period too narrow for 
their requirements, Ican see no reason on the geological side why 
they should not be at liberty to enlarge it as far as they may find 
to be needful for the evolution of organised existence on the 
globe. As I have already remarked, it is not the length of time 
which interests us so much as the determination of the relative 
chronology of the events which were transacted within that time. 
As to the general succession of these events, there can be no 
dispute. We have traced its stages from the bottom of the 
oldest rocks up to the surface of the present continents and the 
floor of the present seas. We know that these stages have 
followed each other in orderly advance, and that geological 
time, whatever limits may be assigned to it, has sufficed for the 
passage of the long stately procession. 
We may, therefore, well leave the dispute about the age of 
the earth to the decision of the future. In so doing, however, 
I should be glad if we could carry away from it something of 
greater service to science than the consciousness of having 
striven our best in a barren controversy, wherein concession 
has all to be on one side and the selection of arguments entirely 
on the other. During these years of prolonged debate I have 
often been painfully conscious that in this subject, as in so many 
others throughout the geological domain, the want of accurate 
numerical data is a serious hindrance to the progress of our 
science. Heartily do I acknowledge that much has been done 
in the way of measurements and experiments for the purpose of 
providing a foundation for estimates and deductions. But in- 
finitely more remains to be accomplished. The field of investi- 
gation is almost boundless, for there is hardly a department of 
geological dynamics over which it does not extend. The range 
of experimental geology must be widely enlarged, until every 
process susceptible of illustration or measurement by artificial 
means has been investigated. Field-observation needs to be 
supplemented where possible by instrumental determinations, 
so as to be made more precise and accurate, and more capable 
of furnishing trustworthy numerical statistics for practical as well 
as theoretical deductions. 
The subject is too vast for adequate treatment here. But let 
me illustrate my meaning by selecting a few instances where 
the adoption of these more rigid methods of inquiry might 
powerfully assist us in dealing with the rates of geological pro- 
cesses and the value of geological time. Take, for example, 
the wide range of lines of investigation embraced under the 
head of Denudation. So voluminous a series of observations 
has been made in this subject, and so ample is the literature 
devoted to it, that no department of geology, it might be 
thought, has been more abundantly and successfully explored. 
Yet if we look through the pile of memoirs, articles and books, 
