114 Major-Gen. McMahon — Culm-measures at Bude, Cornwall. 



tained fragments of such rocks. The sand of the existing Panjab 

 rivers, and the Sivalik beds, the product of Panjah rivers in the 

 Tertiary period, abound in fragments of slate and limestone. 



As a rule, I presume, heavy minerals are carried down by the 

 main stream of a river, and the lighter ones are floated off over its 

 banks to flood the country on either side of it ; but this explanation 

 can hardly be applied to the Bude rocks, as it would fail to account 

 for the absence of. such rocks as slate and limestone, on the one 

 hand, or the presence of such minerals as schorl (sp. g. 3 — 3 - 24) 

 and zircon (sp. g. 4 - 4 — 4-7) on the other. If schorl and zircon could 

 have been floated to Bude, why not hornblende and other minerals ? 



Mr. A. W. Stokes, F.C.S., F.I.C., was good enough to make an 

 analysis of one of the Bude samples for me, which I give below as 

 No. I. The specimen was a slaty-looking shale. 



100-00 100-39 100-54 



* Obtained by heating to 120° C. for four hours. 



I have for the purposes of comparison given under II. and III. 

 the analyses of two British granites made by Mr. J. A. Phillips, 

 quoted by Mr. J. J. Harris Teall in his British Petrography, pp. 

 311, 314. I have selected these two because they come close to the 

 analyses of the Bude rock in the per-centage of silica. II. and III. 

 contain only a trace of magnesia, but in other analyses of granites 

 made by Mr. J. A. Phillips this constituent rises to nearly 2 per cent. 



An examination of the above analysis of the Bude shale bears out, 

 I think, the result of the microscopic investigation. It seems to me 

 to support the view that the silt deposited by the Bude waters was 

 made up of granitic materials supplemented on the spot by the 

 products of organic life, carbon, and iron ; the carbon being derived 

 by organic processes from the air, and the iron from the water. 



One more point remains for consideration. Beyond all question 

 the Bude rocks have, since their consolidation, been subjected to 

 great lateral. pressure, contortion, and crushing. On the other hand, 

 it is equally certain that they could not by any stretch of the 

 imagination be called metamorphic, or metamorphosed, rocks. But 

 if dynamic force is capable of producing the metamorphic change's 

 claimed for it by the exponents of dynamic metamorphism, how is 

 it that the Bucle beds are not metamorphosed ? This is, I think, 

 a pertinent question directly raised by the Bude beds, and one that 

 is worth some serious consideration. 



In offering a few concluding remarks on this subject, I propose 



