214 LAY SERMONS, ESSAYS, AND REVIEWS. [xi. 



for believing in the slow rate of the change in living forms is the 

 fact that they persist through a series of deposits which, geology 

 informs us, have taken a long while to make. If the geological 

 clock is wrong, all the naturalist will have to do is to modify his 

 notions of the rapidity of change accordingly. And I venture to 

 point out that, when we are told that the limitation of the period 

 during which living beings have inhabited this planet to one, 

 two, or three hundred million years requires a complete revolu 

 tion in geological speculation, the onus yrdbandi rests on the 

 maker of the assertion, who brings forward not a shadow of 

 evidence in its support. 



Thus, if we accept the limitation of time placed before us by 

 Sir W. Thomson, it is not obvious, on the face of the matter, 

 that we shall have to alter, or reform, our ways in any appreciable 

 degree ; and we may therefore proceed with much calmness, and 

 indeed much indifference, as to the result, to inquire whether 

 that limitation is justified by the arguments employed in its 

 support. 



These arguments are three in number : 



I. The first is based upon the undoubted fact that the tides 

 tend to retard the rate of the earth s rotation upon its axis. That 

 this must be so is obvious, if one considers, roughly, that the 

 tides result from the pull which the sun and the moon exert 

 upon the sea, causing it to act as a sort of break upon the rotating 

 solid earth. 



Kant, who was by no means a mere &quot; abstract philosopher,&quot; 

 but a good mathematician and well versed in the physical science 

 of his time, not only proved this in an essay of exquisite clear 

 ness and intelligibility, now more than a century old, 1 but 

 deduced from it some of its more important consequences, such 

 as the constant turning of one face of the moon towards the 

 earth. 



1 &quot; Untersuchung der Frage ob die Erde in ihrer Umdrehung urn die 

 Achse, wodurch sie die Abwecliselnng des Tages und der Nacht hervor- 

 bringt, einige Veranderung seit den ersten Zeiten ihres Ursprunges erlitten 

 habe, &c.&quot; KANT S Sammtliche Werke, Bd. i. p. 178. 



