280 Journal of the Asiatic Society of Bengal. [July, 1914.] 



corresponding figures are respectively 66 6 and 33*3 per cent. 

 In certain cases no doubt all the figures have the same sign, 

 but I think — I cannot confirm this, as I have not the paper 

 with me — that similar groups will be found among my figures. 

 But in neither case — that of Major Crosthwait's results or that 

 of mine— would my temperament be sufficiently sanguine to 

 allow to me to say, as Colonel Lenox-Conyngham does of the 

 former, that " there was a very strong tendency to persistence 

 of sign." 



In my discussion of the ' rift hypothesis,' I purposely 

 avoided confusing the issue by any detailed consideration 

 of Colonel Burrard's further ingenious suggestion as to the 

 occurrence of other " subcrustal " cracks. So far as its ori- 

 ginal purpose is concerned, the suggestion has now probably 

 become unnecessary, since the more usual hypothesis as to the 

 nature of the Indo Gangetic depression appears capable of 

 accounting for the various geodetic anomalies. The new hypo- 

 thesis is undoubtedly a convenient one, since it is capable of 

 infinite adaptability, any individual anomaly being removable 

 by the postulation of a suitable crack: unfortunately, it is 

 unsupported by other evidence and until the accepted hypo- 

 thesis, which is based on solid foundations in other respects as 

 well, has been shown to be inadequate on geodetic grounds, it 

 would be difficult to justify the introduction of a new one. At 

 the same time Colonel Burrard's interesting application of his 

 idea to tectonic processes cannot fail to attract attention and 

 will no doubt receive careful consideration. His suggestion 

 that the opening of a crack may result in the folding of the 

 overlying material and so produce mountain ranges is difficult 

 of investigation to the extent required to remove it from the 

 realm of conjecture. Subterranean cracks are of course fami- 

 liar phenomena ; those that would seem of sufficient importance 

 to produce the required effect are always found to contain 

 intrusive igneous material, which is believed with good show 

 of reason to have been injected contemporaneously with the 

 formation of the crack. The problem thus becomes an ex- 

 tremely complicated one and will require very extensive investi- 

 gation before it can hope to supplant the elaborate structure 

 built up by Professor Joly with such ingenuity and detail and 

 based on such extensive observations of mountain structure. 



