202 
at present, and that if we look far enough back we must 
inevitably come to an epoch when the moon would seem 
' to have been quite close to the earth; indeed looking 
earlier still we are not without reasons for believing that 
in primeval times the earth and the moon formed but a 
single body. 
Wondrous as this narrative may seem, yet on a due 
consideration of the mathematical evidence in its favour 
we are constrained to admit that it must be substantially 
correct. Unless some notable agency at present unknown 
to us has intervened in past time, the course of events 
must have run along the lines we have indicated. We 
make but little pretence to give the date when the moon 
seems to have commenced its independent existence, nor 
to indicate the chronology of the epochs when its distance 
increased by one thousand miles after another. All that 
seems certain is that the events we are at present dis- 
cussing must have occurred millions, many millions of 
years before man placed his foot on this planet. 
The cause of these mighty series of changes is still in 
hourly operation. The ebb and flow of the tides around 
our coasts is only the survival of greater tides with which 
in earlier days the ocean must have throbbed. The 
earlier we look back the mightier must have been the 
daily ebb and flow. I even invited you to look back to 
an excessively remote epoch when the moon was only at 
a fraction of its present distance, and when the daily rise 
and fall, instead of being counted in tens of feet, must 
have been reckoned by hundreds. Even up to this point 
there has been little or no controversy, there can be none. 
I do not know that any one has attempted to deny that 
the earth must once have experienced these mighty tides 
either in the actual body of the earth, or in the ocean on 
its surface. The controversy has arisen on the question 
as to whether these great tides had subsided before the 
commencement of the geological epoch, or whether they 
were contemporaneous therewith. 
In my lecture in this hall last year, I made the sug- 
gestion that the reign of the mighty tides did perhaps 
extend into the commencement of the geological epoch. 
I further ventured to suggest that these great tides had 
left their traces on the solid crust of the earth. I qucted 
eminent geological authority to show that the rocks at the 
base of our stratified system are of the most stupendous 
volume and thickness. It has always been a difficulty to 
determine how the present geological agents could 
have manufactured so mighty a mass, and I appealed to 
the great tides as a grinding engine competent to aid in 
this work. At this point issue has been taken, and it is 
now my duty to review the arguments which have been 
adduced as bearing on this question. 
objections that have been raised. 
critics do not seem to have observed that I postulated 
the mighty tides for the manufacture of the earliest 
primeval rocks, and for these alone. “Take, for ex- 
ample,”’ I said (p. 25), ‘‘that earliest and most interesting 
epoch when life perhaps commenced on the earth, and 
when stratified rocks were deposited five or ten miles 
thick, which seem to have contained no living form 
higher than the eozoon, if even that were an organised 
being.” Again and again I stated that I merely referred 
to these primitive strata. Yet this is a point that many 
of my critics have ignored. They have been at pains to 
prove that colossal tides did not exist in the compara- 
tively modern geological epochs, and many interesting 
facts have been adduced. But such considerations have 
only an infinitesimal bearing on the position I adopted. 
Even the coal-measures are a modern formation when 
compared with the primeval rocks, for the manufacture of 
which I suggested the mighty tides. 
The controversy as to the great tides has principally 
ranged around the question as to whether the primitive 
rocks present any indications of great tidal action. Iam 
NATURE 
But let me here | 
make a single remark which disposes of many of the | 
Several of my | 
[ Dec. 28, 1882 
not a practical geologist, and am most anxious to obtain 
the views of those that are. Now these opinions are to 
be had. They are to be found in the corresponcence in. 
NATURE at the commencement of this year ; yet there 
is, as might have been anticipated, considerable differ- 
ences of opinion. I first refer to Prof. Hull’s letter 
(NATURE, vol. xxv. p. 177), and find that this most com- 
petent authority adduces direct evidence of tremendous 
denudation in the Palaeozoic ages, such as might have 
been produced by mighty tides. On the other hand, 
Prof. Newberry (vol. xxv. p. 357) says that there is no 
direct evidence whatever to show that the denuding agen- 
cies were greater in forrer times than now. In the 
following number of NATURE we have letters from Dr. 
Callaway and Mr. Hale (p. 385) to show that Prof. New- 
berry’s conclusions are not necessarily valid. Mr. S. V- 
Wood and Mr. J. Vincent Elsden bring forward facts 
which go to support Prof. Newberry’s view, while Dr. 
Callaway, though carefully declining to commit himself 
to the high tides, controverts Mr. Wood and Mr. Elsden 
(p. 409). Now all these gentlemen speak with special 
knowledge, but it is not easy to deduce from this corre- 
spondence as to which side the balance of skilled opinion 
really inclines. It would almost seem as if a very funda- 
mental point had escaped attention. Prof. Geikie, in his 
great work just published, tells us that these great tides 
could not have existed in geological times, because, if 
they had done so they must have left certain traces, and 
we do not find these traces. The fundamental question 
is, What traces of great tides ought we to expect to 
find if those great tides had really existed? It would 
seem that unless this question be first answered, it is im- 
possible to dispose of the question with the brevity 
which Prof. Geikie has adopted. {1 apprehend it cannot 
be doubted that by the great tides the materials of strati- 
fied rocks would be rapidly formed, and that in suitable 
localities these materials would be deposited to form 
rocks. I can see no necessary difference between a ton 
of mud ground up by colossal agents in former days, and 
a ton of mud ground up by the more prosaic agents of 
modern days. But for each ton of mud now made there 
would then have been a great many tons. The strata 
would thus have grown more rapidly in early times, and 
thus the exceptional thickness of the earliest stratified 
rocks could be accounted for. It seems useless to assert 
that vestiges of the great tides do not exist, unless we 
can form some idea of the sort of vestiges that should be 
expected if the great tideshad existed. I believed at the 
time I gave my lecture, and I believe still, that we do see 
vestiges of vast primzeval tides. I can even count these 
vestiges, They are five, or perhaps ten in number ; they 
are the five or ten miles of vertical thickness of stratified 
rocks which were deposited at the bottom of the ocean 
during the earliest stages of the geological epoch. 
I have derived so much pleasure and so much in- 
struction from the study of Mr. G. H. Darwin’s writings, 
that on this ground alone I would be reluctant to have any 
difference of opinion with him. Indeed, seeing that the 
earth-moon history is one which he has made peculiarly 
his own, and illuminated by discoveries which I believe 
to be the most important contributions made to physical 
astronomy in modern times it would seem presumption in 
me to venture to differ from him. Mr. Darwin, writing in 
NATURE, vol xxv. p. 213, has asked me to reconsider the 
views I had set forth as to the probability of the great 
tides being contemporaneous with geological phenomena. 
Mr. Darwin shows that at the time when the great tides 
supposed in my calculation existed, the earth must have 
been spinning round once in seven hours, and that this 
would involve trade-winds of 3#times their present velocity 
and vertical storms of prodigious violence, and then 
he adds :— 
“Now if this state of things existed in geological 
history, we should expect to find the earlier sedimentary 
