PROFESSOR HUXLEY'S LECTURES. 45 



things has had only a limited duration, and that at some period in the 

 past the state of things which we now know (substantially, though not, 

 of course, in all its details) arose and came into existence without any 

 precedent condition from which it could have naturally proceeded. 

 The third hypothesis also assumes that the present order of Nature 

 has had but a limited duration, but it supposes that the present order 

 of things proceeded by a natural process from an antecedent order, 

 and that from another antecedent order, and so on ; and on this hy- 

 pothesis the attempt to fix any limit at which we could assign the 

 commencement of this series of changes is given up. I am very 

 anxious that you shall realize what these three hypotheses actually 

 mean ; that is to say; what they involve, if you can imagine a spec- 

 tator to have been present during the period to which they refer. On 

 the first hypothesis, however far back in time you place that specta- 

 tor, he would have seen a world essentially, though not perhaps in all 

 its details, similar to that which now exists. The animals which ex- 

 isted would be the ancestors of those which now exist, and like them ; 

 the plants in like manner would be such as we have now; and the 

 supposition is that, at however distant a period of time you place your 

 observer, he would still find mountains, plains, and waters, with ani- 

 mal and vegetable products flourishing upon them and sporting in 

 them just as he finds now. That view has been held. It was a favor- 

 ite fancy of antiquity, and has survived toward the present day. It 

 is worthy of remark that it is an hypothesis which is not inconsistent 

 with what geologists are familiar with as the doctrine of Uniformita- 

 rianism. That doctrine was held by Hutton, and in his earlier days 

 by Lyell. For Hutton was struck with the demonstration of astrono- 

 mers that the perturbations of the planetary bodies, however great 

 they may be, yet sooner or later right themselves, and that the solar 

 system contained within itself a self-adjusting power by which these 

 aberrations were all brought back to an equilibrium. 



Hutton imagined that something of the same kind may go on in 

 the earth, although no one recognized more clearly than he the fact 

 that the dry land is being constantly washed down by rain and rivers 

 and deposited in the sea, and that thus in a certain length of time, 

 greater or shorter, the inequalities of the earth's surface must be 

 leveled, and its high lands brought down to the sea. Then, taking into 

 account the internal forces of Nature, by which upheavals of the sea- 

 bottom give rise to new land, he thought that these operations might 

 naturally compensate each other, and thus, for any assignable time, 

 the general features of the earth might remain what they are. And, 

 inasmuch as there need be no limit under these circumstances to the 

 propagation of animals and plants, it is clear that the logical develop- 

 ment of this idea might lead to the conception of the eternity of the 

 world. Not that I mean to say that either Hutton or Lyell held this 

 conception assuredly not ; they would have been the first to repu- 



