C. Lloyd Morgan — Geological Time. 205 



at the rate of -2V of an inch per annum ; then the time occupied in 

 the deposition of 100,000 feet of rock would be eighty-two and a 

 half millions of years. Seeing therefore that, in the first place, 

 100,000 feet is probably too high an estimate of the average thick- 

 ness of the rocks from Laurentian times to the present ; that, in the 

 second place, those rocks should be more properly arranged in two 

 or three parallel series than in one long column ; that, in the third 

 place, the rate of deposit, on which the calculation is made, is 

 sufficiently small ; and that, lastly, on the evolution hypothesis, 

 there is some probability that, in old geological times, the strata 

 were formed more rapidly than in these latter days, is there any 

 reason why geologists should hesitate to accept 100,000,000 years 

 as the limit of geological time? Nay, for my own part I shall 

 not, on geological grounds, feel very uneasy if more certain physical 

 results than have already appeared limit the age of the rocks to fifty 

 millions of years. 



An attempt has been made by Mr. T. Mellard Eeade to estimate 

 the geological age of the earth by the amount of chlorides con- 

 tained in solution by sea- water. "Eeckoning all the chlorides 

 annually brought into the sea at eight tons to the square mile, it 

 would take," he says, " in even numbers, two hundred millions of 

 years to renew the chlorides of the sea." How far these figures 

 may be correct it is not easy to say. We have at present but few 

 data bearing upon the subject. But supposing, with Mr. Eeade, 

 that it would take, at the present rate, two hundred millions of years 

 to restore to the sea its saline constituents, then, taking into con- 

 sideration the exceedingly soluble nature of these chlorides, and 

 the high probability that in ancient geological times, when the earth 

 was younger, these materials were washed seawards far more rapidly 

 than is at present the case, it would seem a fair conclusion that from 

 sixty to one hundred millions of years have been amply sufficient to 

 render, by these means, the sea as salt as we now find it. 



" But it may be said," writes Professor Huxley, "■ that it is biology, 

 and not geology, which asks for so much time — that the succession 

 of life demands vast intervals ; but this appears to me," continues 

 the Professor, " to be reasoning in a circle. Biology takes her time 

 from Geology. The only reason we have 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." Professor Young, also, in his Presidential 

 Address, British Association, Section C, speaks of Biologists " who, 

 apparently unconsciously, seek to gain, by prolonging the interval 

 between successive groups the time which ought rather to be sought 

 for in tracing, were that possible, the migrations of the species 

 which seem to have suddenly died out." 



!s?i The biological aspect of Geological Time is, however, in my 

 opinion, that which most authoritatively prevents us from accepting 

 the " ten or fifteen million of years " which is all Professor Tait's 



