434 Rev. 0. Fisher — "The Origin of Mountains" : a Reply. 



therefore in favour of its natural association. If so, it is reasonable 

 to suppose that the skull will ])rove to be that of a very primitive 

 type, not that of a highly civilized man. I have accordingly made 

 a new study of the specimen, with the special help of my colleague, 

 Mr. W. P. Pycraft, and I find that tlie only alteration necessary in 

 my original model (made by Mr. Frank 0. Barlow) is a very slight 

 displacement of the occipital and right parietal bones, which 

 Professor Elliot Smith pointed out to me when he made his first 

 studies of the brain. Both behind and in front I correctly identified 

 the internal groove for the upper longitudinal blood-sinus, which 

 marks the middle line of the roof of the skull ; and the reason why 

 my adjustment of the occiput was not exact at first is, that on 

 the hinder part of the parietal region of the skull-roof I noticed 

 a longitudinal ridge which I supposed to be truly median, while the 

 extraordinarily unsymmetrical development of the brain seemed to 

 have pushed the longitudinal sinus at that part slightly out of its 

 normal place. I now know that the longitudinal ridge is one of 

 a pair. The change, however, only opens the upper part of the skull 

 behind to an extent of three-quarters of an inch, and there are 

 compensations elsewhere through the necessary readjustments, so the 

 total brain capacity remains nearly the same as that I originally 

 stated, well within the range of the smallest human brains of the 

 present day. 



I may add that I have submitted the new brain-cast to Professor 

 Elliot Smith, who allows me to state that he finds it in all essential 

 respects correct. He will shortly describe it in a memoir on fossil 

 human brains to be read before the Royal Society. 



EXPLANATION OF PLATE XV. 

 EOANTHROPUS Dawsoni, A. S. Woodw. ; from a Pleistocene gravel near 



Piltdown Common, Fletching, Sussex. 

 Fig. 1. Eight side-view of skull and mandible. One-third nat. size. 

 ,, 2. Outer view of right mandibular ramus, with the canine tooth placed in 

 natural position. Two-thirds nat. size. 



I 



II. — "The Origin of Mountains": a Reply. 



By the Eev. 0. Fisher, M.A., F.G.S. 



AM content to leave to the readers of the Geological Magazine 

 the question whether Colonel Burrard's theory of the elevation 

 of mountains and Mr. Hayford's of the distribution of density to 

 cause isostasy are more in accordance with geological phenomena 

 than my theory of mountain roots supported in a dense liquid 

 substratum. But in Colonel Burrard's reply ^ to my j^aper in the 

 Magazine for June there is a fundamental but specious error. 

 I wrote : " Is it not possible that the earth's rotation may impart to it 

 a ' gyroscopic ' quasi rigidity, which may enable it to withstand the 

 deforming influence of external forces [the attraction of the moon 

 aud sun], although at the same time forces internal to the earth will 



^ This Magazine, September, 1913. 



