Notices of Memoirs — A Fossil Cycad, Portland. 313 



under pressure along lines of least resistance. On the other 

 hand, if the rock is really a granite all through, that is to say, the 

 product of a molteil magma drawn from some unknown underground 

 reservoir, then its activities as an intrusive rock have been kept 

 well under control." 



Whichever of the two views stated by the author be adopted, it is 

 clear that there must have been a reservoir of molten or semi-molten 

 rock at the root of the Himalayas sufficiently capacious to have 

 supplied the enormous masses of gneissose-granite now to be found 

 along the whole length of these mountains, for it is admitted that 

 the granite came into place as an intruder, and it is not suggested 

 that sedimentary rocks were heated up and converted into granite 

 in situ. The author speaks of the " granitic foundations out of 

 which the Himalaya were ultimately to rise " (p. 275) — that, by the 

 way, sounds rather like my own view which the author contests — and 

 he contrasts them with the "gneisaic foundations of the peninsula 

 of India " (p. 275) ; and the author remarks with reference to the 

 theory of those who assert the Archeean age of the gneissose-granite, 

 "even they must admit a pretty thorough mixing of the material by 

 some agency before it quietly found its way in an intrusive capacity 

 among the ancient sedimentary rocks " (p. 276). 



The author's views, then, involve the supposition that immediately 

 preceding the intrusion of the granite there was a reservoir of 

 molten or semi-molten rock forming " the granitic foundations out of 

 which the Himalaya were ultimately to rise." That being so, what, 

 I would ask, would be the result of powerful tangential pressure 

 applied to the sides of this reservoir ? Would not the granite " rise 

 along the line of least resistance " ? This rise of the granite, the 

 author tells us, took place " under such enormous pressure of the 

 superincumbent rocks that an eruptive function was generally denied 

 it" (p. 274), and "it was formed as great laocolites." That being 

 so, would not granite moved upwards with sufficient force to over- 

 come the " enormous pressure " that tried in vain to keep it down, 

 have elevated the rocky cover? I think such elevation would, under 

 the conditions supposed, be inevitable, and that I was therefore fully 

 justified in stating that "the contortion, compression, and upheaval 

 of the Himalayas were connected with the intrusion of the gneissose- 

 granite." 



{To he continued.) 



ZSTOTiaES OIF DNvCEHVLOIIEaS- 



I. — A New Fossil Cyoad from the Isle of Portland. 

 (PLATES XIII AND XIV.) 



AN example of a Jurassic Cycadean stem of exceptional interest 

 has lately been added to the Fossil Plant Gallery of the British 

 Museum. The specimen is described in detail by Mr. A. C. Seward 

 in the Quarterly Journal of the Geological Society for February of 

 this year. 



