28 TRAPS AND INTERTRAPPEAN BEDS 



is always inserted either between the strata of the inter trappeans or 

 between them and the underlying- rock, frequently Damuda or Mahadeva 

 sandstone and shale, and never between the beds of the latter ? Lastly, 

 the idea of a mass of fluid, such as liquid lava, being- intruded throughout 

 immense distances, in this case for hundreds of miles, between two 

 pre-existing strata, instead of forcing its way to the surface through 

 the fh'st crack it meets with, is, to my mind, opposed to the first principles 

 of physics. Any fluid forced up from below, be it liquid lava, or 

 water, or gas, will unquestionably follow the course in which it meets 

 with least resistance, the " line of weakness^' in short. How can this 

 be a horizontal fracture of immense extent, by intrusion into wliich 

 not only enormous friction has to be overcome, but the whole superin- 

 cumbent mass of rock has to be lifted bodily ? Meantime the surface 

 of the earth is only a few hundred feet above, and all that is to be 

 overcome to reach it is the friction produced by the lateral pressure of 

 the walls of any vertical crack, a resistance diminishing with every foot 

 of rise. If the earth^s surface be many thousands of feet above, instead 

 of a few hundreds, the argument is so much the stronger ; with the 

 increased pressure the resistance to horizontal intrusion will augment 

 in every instance, and the easiest road for the pent up fluid to escape 

 must be the shortest leading to the surface. This argument is suscepti- 

 ble of very wide application. If all geologists would bear it in mind 

 when studying igneous rocks, we should hear very much less of granitic 

 and volcanic '' intrusions'^ than is the case at present, and we should, 

 I suspect, find that instead of being the most prevalent and eflTective, 

 they are amongst the least important of the forces which operate and 

 have in past times operated to change the surface of the globe. 



I believe, then, that Mr. Hislop's, and I may add. Dr. Carter's* 

 theory of the horizontal intrusion of beds of trap is not only opposed 



* Sec Jouv. Bombay Br. Roy. As. Soc, Vol. V, p. 257-2&8. 

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