414 
TOPULAR SCIENCE REVIEW. 
we could not have a better instance than that afforded by Mr. Darwin, in 
quoting from the article on “ Death-Rate,” in his last work on “ The 
Descent of Man,” and in mentioning Dr. Farr’s special opinion as to the 
quality of the paper quoted from. Of the numerous chapters in the work 
it is impossible for us to speak specially: suffice it to state the subjects 
of a few. Thus we have “ Strange Discoveries respecting the Aurora,” 
“ Our Chief Time-piece Losing Time,” “ Recent Solar Researches,” “ Secret 
of the North Pole,” “A Great Tidal Wave,” “ Deep-Sea Dredgings,” 
“Tunnel through Mont Cenis,” “Earthquake* in Peru,” “A Shower of 
Snow Crystals,” “ Influence of Marriage on the Death-Rate,” “ The Safety 
Lamp,” “Photographic Ghosts,” “ Betting on Horse Races,” “Squaring the 
Circle,” and a new theory of “ Achilles’ Shield.” These are but a few of 
many articles, but they strike us as among the most important. Especially 
interesting, however, of all these is the paper on “ Our Chief Time-piece 
Losing Time.” This is both a remarkable and an interesting article. It 
relates to the fact that the motion of the earth is gradually altering, so 
slowly of course* that it is almost imperceptible, but still decidedly. This 
change relates to> the form of the earth’s orbit, which, with regard to the 
motion of the moon, is decidedly undergoing a change. Of course this is 
an alteration of not the least importance in a practical point of view; but 
it is one which is of importance astronomically, and which is most mar- 
vellous as illustrative of the wonderful accuracy of modem research. 
“ Suppose,” says Mr. Proctor, “that, just in front of our moon a false 
moon, exactly equal to ours in size and appearance, were to- set off with a 
motion corresponding to the present motion of the moon, save only in one 
respect, namely — that the false moon’s motion should not be subject to the 
change we are considering, termed the acceleration. Then one hundred years 
would elapse before our moon would fairly begin to show in advance. She 
would in that time have brought only one one-hundred-and-fiftieth part 
of her breadth from behind the false moon. At the end of another century 
she would have gained four times as much ; at the end of a third, nine 
times as much ; and so on. She would not fairly have cleared her own 
breadth in less than twelve hundred years. But the whole ■ of this gain, 
minute as it is, is not left unaccounted for by our modern astronomical 
theories. Half the gain is explained, the other half remains to be inter- 
preted ; in other words, the moon travels further by about half her own 
breadth in twelve centuries than she should do according to the lunar theory. ” 
But what, we may ask, is the cause of this singular retardation, if so it 
be, of the earth’s rotation-movement ? The cause would appear to be, 
according to Mr. Proctor, the movement of the tides. And a little reflec- 
tion will serve to convince anyone who doubts it that here is an expenditure 
of a very considerable degree of power, of indeed in some cases an enor- 
mous degree of almost unassailable force. Now where, asks Mr. Proctor, 
does this force come from? “ Motion being the great ‘force-measurer,’ 
what motion suffers that the tides may work? We may,” he thinks, 
“ securely reply that the only motion which can supply the requisite force 
is the earth’s motion of rotation.” Therefore, he says, it is no idle dream, 
but a matter of absolute certainty that, though slowly, still very surely, 
oi] r terrestrial plobe is losing its rotation-movement. Other chapters in the 
