72 R. D. Oldham — Essays in Theoretical Geology. 



in coarseness of texture in the upper beds as compared with the 

 lower.^ 



Besides these two borings, one has been put down at Agra, the 

 evidence of which is slightly vitiated by the peculiar local conditions. 

 The abstract of the section is as follows ; ^ — 



Here there would seem to be an increase of coarseness of texture, 

 both upwards and downwards, from 200 feet. The expLanation of 

 this, I apprehend, is to be found in the fact that the surface deposits 

 round Agra are largely convposed of blown sand ; and it is probable 

 that the sand beds found in the uppermost 160 feet of the section are 

 of ^olian origin, while below that the beds are alluvial and exhibit 

 the gradual upward increase in fineness of texture required by the 

 hypothesis. 



A fourth boring has lately been sunk to a depth of 1336 feet 

 at Lucknow. As might be expected from its situation, " there is 

 no marked increase or decrease in the coarseness of the beds passed 

 through ; but, near the bottom of the boring, some beds of coarse 

 sand were found, and these may indicate an approach to the base 

 of the alluvium and mai'k a time when its southern boundary was 

 not far from Lucknow." 



To sum up, of the four deep borings which have been made, 

 two are completely in accordance with the hypothesis ; one is in 

 favour of it, though its evidence is vitiated by peculiar local condi- 

 tions ; while the fourth is so situated as to give no evidence one 

 way or the other till it is carried to a greater depth. Stronger 

 proof is at present impossible, and we may accept the hypothesis 

 as a true one. 



To summarize the history of the Himalayas as revealed by their 

 geology, we find that at the commencement of the Secondary period 

 the Himalayan system of disturbance had not commenced; that, 

 some time towards the end of the Secondary period, it originated 

 near the middle of the range and gradually extended outwards, 

 reaching the country now accessible to observation in the North- 

 western portion of the Himalayas, about the commencement of the 

 Tertiary period ; that the beds had, at this epoch, undergone but 



1 On a former occasion (Rec. Geol. Surv. Ind. vol. xviii. p. 1 1 8) I was misunderstood 

 when urging this argument ; it was pointed out that Umballa is peculiarly situated 

 in an area which receives no coarse deposit ; that, at an equal distance from the foot 

 of the hills, large boulders were found in the foundations of the railway bridge over 

 the Jumna ; and it was urged that the section was consequently irrelevant. Owing 

 to this I must here point out that the argument is by no means affected by the 

 greater or less average coarseness of texture of the deposits on other sections, as it 

 only claims that on any individual section near the northern limit of the plains the 

 beds near the surface will, on the average, have a greater coarseness of texture than 

 those which underlie them. 



'^ For detailed section see Eec. Geol. Surv. Ind. vol. xviii. p. 121. 



