104 
thus contribute their quota to the manufacture of stratified 
rocks. Such is the modest 7é/e which Lyell has assigned 
to the tides, and no doubt the majority of geologists have 
acquiesced in this doctrine. Nor can there be any doubt 
that this is a just view of tidal action at present. That it 
is a just view of tidal action in past times is what I now 
deny. Lyell did not know—Lyell could not have known 
—that our tides are but the feeble surviving ripples of 
mighty tides with which our oceans once pulsated. Intro- 
duce these mighty tides among our geological agents, and 
see how waves and storms, rivers and glaciers, will hide 
their diminished heads. 
I must attempt to illustrate this view of tidal importance 
in ancient geological times. Let me try by the aid of the 
tides to explain the great difficulty which every one must 
have felt in regard to Lyell’s theory. I allude to the 
stupendous thickness of the Paleozoic rocks. 
Look back through the Corridors of Time in the manner 
in which they are presented tous in the successive epochs 
of geology. We pass rapidly over the brief career of pre- 
historic man; then through the long ages of Tertiary 
rocks, when the great mammals were developed ; back 
again to the much earlier period when colossal reptiles 
and birds were the chief inhabitants of the earth; back 
again to those still earlier ages when the luxuriant forests 
flourished that have given birth to the coal-fields; back 
Once more to the age of fishes; back finally to those 
earliest periols when the lowest forms of life began to 
dawn in the Palaeozoic era. 
As we date remote ages astronomically by the distance 
of the moon, so we date remote ages geologically by the 
prevailing organic life. It is a great desideratum to 
harmonise these two chronological systems, and to 
find out, if possible, what lunar distance corresponds 
to each geological epoch. In the whole field of 
natural science there is no more noble problem. Take, 
for example, that earliest and most interesting epoch 
when life perhaps commenced on the earth, and when 
stratified rocks were deposited five or tei miles thick, 
which seem to have contained no living forms higher 
thin the humble Eozoon, if even that were an organised 
being. Let us ask what the distance of the moon was at 
the time when those stupendous beds of sediment were 
deposited in the primeval ocean. We have in this com- 
parison every element of uncertainty except one. The 
exception is, however, all important. We know that the 
moon must have been nearer to the earth than it is at 
present. There are many very weighty reasons for 
supposing that the moon must have been very much 
nearer than it is now. It is not at all unlikely that the 
moon may then have been situated at only a small 
fraction of its present distance. My argument is only 
modified, but not destroyed, whatever fraction we may 
ta.e. We must take some estimate for the purpose 
of illustration. I have had considerable doubts what 
estimate to adopt, I am desirous of making my argu- 
ment strong enough, but I do not want to make it seem 
exaggerated. At present the moon is 240,000 miles away ; 
but there was a time when the moon was only one-sixth 
part of this, or say 40,000 miles away. That time must 
have corresponded to some geological epoch. It may 
have beea earlier than the time when the Eozoon lived. 
It is more likely to have been later. I want to point out 
that when the moon was only 40,000 miles away, we had 
in it a geological engine of transcendent power. 
On the primitive oceans the moon raised tides as it 
does at present ; but the 40,000-mile moon was a far more 
efficient tide-producer than our 240,000-mile moon, The 
nearer the moon the greater the tide. To express the 
relation accurately we say that the efficiency of the moon 
in producing tides varies inversely as the cube of its dis- 
tance. Here then we have the means of calculating the 
tidal efficiency for any moon distance. The 40,000-mile 
moon being at a distance of only one-sixth of our present 
NATURE 
[ Dec. 1, 1881 
moon’s distance, its tidal efficiency would be incfeased 
6X 6x 6fold. In other words, when our moon was 
only 40,000 miles away it was 216 times as good a tide- 
producer as it is at present. 
The heights to which the tides rise and fall is so pro- 
foundly modified by the coasts and by the depth of the 
sea, that at present we find at different localities tides of 
only a few inches and tides of 60 or 70 feet. In ancient 
times there were no doubt also great varieties in the tidal 
heights, owing to local circumstances. To continue our 
calculation we must take some present tide. Let us dis- 
card the extremes just indicated and take a moderate tide 
of 3-feet rise and 3-feet fall as a type of our present tides. 
On this supposition what is to be a typical example of 
a tide raised by the 40,000 mile moon? If the present 
tides be 3 feet, and if the early tides be 216 times their 
present amount, then it is plain that the ancient tides 
must have been 648 feet. 
There can be no doubt that in ancient times tides of 
this amount and even tides very much larger must have 
occurred. I ask the geologists to take account of these 
facts, and to consider the effect—a tidal rise and fall of 
648 feet twice every day. Dwell for one moment on the 
sublime spectacle of a tide of 648 feet high, and see what 
an agent it would be for the performance of geological 
work! Weare now standing, I suppose, some 500 feet 
above the level of the sea. The sea is a good many 
miles from Birmingham, yet if the rise and fall at the 
coasts were 648 feet, Birmingham might be as great a 
seaport as Liverpool. Three quarters tide would bring 
the sea into the streets of Birmingham. At high tide 
there would be about 150 feet of blue water over our 
heads. Every house would be covered, and the tops of a 
few chimneys would alone indicate the site of the town. 
In a few hours more the whole of this vast flood would 
have retreated. Not only would it leave England high 
and dry, but probably the Straits of Dover would be 
drained, «nd perhaps even Ireland would in a literal 
sense become a member of the United Kingdom. A few 
hours pass, and the whole of England is again inundated, 
but only again to be abandoned. 
These mighty tides are the gift which astronomers have 
now made to the working machinery of the geologist. 
They constitute an engine of terrific power to aid in the 
great work of geology. What would the puny efforts of 
water in other ways accomplish when compared with 
these majestic tides and the great currents they produce? 
In the great primeval tides will probably be found the 
explanation of what has long been a reproach to geology. 
The early paleozoic rocks form a stupendous mass of 
o2zean-mate beds which, according to Prof. Williamson, 
are twenty miles thick up to the top of the silurian beds. 
It has long been a difficulty to conceive how such a 
gigantic quantity of material could have been ground up 
and deposited at the bottom of the sea. The geologists 
said, “ The rivers and other agents of the present day 
will do it if you give them time enough.” But unfor- 
tunately the mathematicians and the natural philosophers 
would not give them time enough, and they ordered the 
geologists to “hurry up their phenomena.” The mathe- 
maticians had other reasons for believing that the earth 
could not have been so old as the geologists demanded. 
Now, however, the mathematicians have discovered the 
new and stupendous tidal grinding-engine. With this 
powerful aid the geologists can get through their work 
in a reasonable period of time, and the geologists and the 
mathematicians may be reconciled. 
I have here a large globe to represent the earth, and a 
small globe suspended by a string to represent the moon. 
At the commencement of the history the two globes were 
quite close; they were revolving rapidly, and the moon 
was constantly over the same locality on the primeval 
earth. I do not know where that locality was; it was 
probably the part of the earth from which the moon had 
