LOGIN NORTH-INDIAN GEOLOGICAL CHANGES. 189 



■whicb. gives rise, I believe, to the very remarkable phenomenon to 

 be seen at IJmballa after a heavy fall of rain — namely, a cracking 

 and subsidence of the ground, forming often chasms large enough to 

 bury a horse or, at times, even an elephant, and which may endanger 

 the public buildings. 



This subsidence is, I believe, owing to the water being drained off 

 from between the particles of sand. During a shower, water from 

 some of the surface -drains or any hollow finds a passage to this dry 

 stratum below, and, flowing with considerable velocity to fill the 

 open spaces formerly deprived of water, disturbs the sand, carries 

 some of it forward ; and thus a chasm is formed into which the 

 superincumbent earth falls, causing the cracks above mentioned*. 

 How this should be met is a difficult question ; and various opinions 

 have been given ; but this I do not at present mean to discuss. 



"WTiat I wish to show is why Umballa is year by year, I understand, 

 becoming more and more deficient of water, which led to the boring 

 of the Artesian well. 



It is necessary to point out what is going on at present before 

 attempting to go back to anterior periods ; but before quitting this 

 part of the subject and passing to theory, it will be better to state a 

 few more facts regarding the effects now being produced by our 

 mountain-torrents f. 



It has been already said that the streams are rapid, broad, and 

 shallow, that during floods they are always overflowing their beds, 

 and depositing the heavier or sandy matter near their banks, while 

 the lighter or clayey matter is carried further towards the secondary 

 streams and is gradually deposited over the plain, so that in time, 

 beds of clay of considerable thickness come to be formed. In the 

 mean time, however, the sandy beds and banks are rising at a more 

 rapid rate ; and they rise so high above the neighbouring country 

 that any slight obstruction, such as a few bushes or a tree, might 

 turn the whole course of a large stream. The torrent thus deserts 

 its old channel and takes to the neighbouring low ground through 

 Avhich the secondary class of streams before alluded to flowed. Thus 

 there is very soon a deposit of sand over the clay. 



With such an arrangement at work it is evident that one may 

 have alternate strata of sand and clay of irregular thickness ; for the 

 torrents which formerly passed down the channels A and B (fig. 2) 

 having raised themselves above the general level of the country, 

 suddenly burst their banks and take to the lower ground at A' and 

 B', which in course of time get settled in their turn. Thus in the course 

 of ages we have a general raising of the land above the sea. 



There is still another way in which this irregularity of deposits 



* In the JuBe Number of ' Chambers's Journal ' I find the following in the 

 " Notes on Science and Art " : — " One consequence of drawing away the water is 

 that the land shrinks. In Tynne many of the houses are settling, the bridges 

 are weakened, and the Corn Exchange is sliding from its front. Similar effects 

 of improved drainage have occurred in other parts of the kingdom." 



t The celebrated Eennell, in the 'Journal of the Asiatic Society,' gave a 

 drawing of the changes of Indian rivers ; and A. Tylor, in the ' Phil. Mag.' for 

 1853, attributed the movements of the channels to unequal rainUxll. 



