124 G. W. JBulman — The Geological Chronometer. 



indication that the strains due to the movements of the sea did not 

 greatly differ in the past." 



But have we any grounds for speaking positively on this point ? 

 Take, for example, the ligaments by which the Brachiopoda are 

 attached to the sea bottom. We can measure the strength of the 

 cable of an existing terebratula, but we have no means of testing the 

 strength of the strand which anchored Terebratula hastata to the bed 

 of the Carboniferous ocean. The actual cable is no longer there ; it 

 is a mere impression, a cast, or chemically altered. And certainly 

 the anchored Mollusca — the Brachiopoda — were more numerous in 

 the early geological ages than other classes, while they are com- 

 paratively rare at the present day. 



Again, Professor Poulton brings forward evidence of a similar 

 kind to show that movements of the air were not greater in the 

 geological past. " We have evidence of a somewhat similar kind to 

 prove uniformity in the movements of the air. The expanse of the 

 wings of flying organisms certainly does not differ in a direction 

 which indicates any greater violence in the atmospheric conditions." 



Quoting the case of the island of Madeira, where an unusually large 

 proportion of the beetles are wingless, and those which fly possess 

 the powers of flight in a higher degree than those on continental 

 areas, he leads us to the conclusion that if there had been greater 

 air currents there would have been a like state of things in the 

 :geological past, with regard to winged creatures in general. 



The evidence is rather slender for the conclusion which is built 

 on it. For, as regards fossil organisms, it is the mere relative 

 expanse of wing we have to go by. But suppose it was set us as 

 a mechanical problem, " Given a flying organism, to fit it for more 

 stormy conditions," how would we endeavour to solve it ? Increase 

 the size of its wings ? That might only the better enable the wind 

 to blow it away. Diminish them ? That would curtail its powers 

 of independent flight. The only solution would appear to be to 

 increase the strength of the muscles, diminish the weight so far as 

 consistent with strength, or alter the shape of the wings. All these 

 things may have occurred in the ancient fliers. 



Again, Professor Poulton quotes Professor G. Darwin to the effect 

 that the size and strength of the trunks of fossil trees afford " evidence 

 of uniformity in the strains due to the conditions of the atmosphere." 

 But I maintain that, although we can measure the size oi a, fossil, we 

 cannot from it accurately gauge the strength of the living organism. 

 The original substance is no longer there, or there only in part. 

 And we know from our existing vegetation how vast a difference 

 there may be in the general form of the trees which are able to stand 

 the present atmospheric strain. But this question of possibly greater 

 atmospheric strain in the past does not seem to be of great importance, 

 as no geologist who has protested against over strict uniformitarianism 

 has laid much stress on it. 



And besides tides and winds, there are other geological agents 

 which may conceivably have been more active in the past. 



(1) Kainfall. There certainly must have been a time when 



