60 OLDHAM : THE CACHAR EARTHQUAKE OF 1 OTH JANUARY 1869. 



In the foregoing pages I have endeavoured to show that, though 

 these apparently vast and striking phenomena are in a certain sense due 

 to the earthquake, they are equally due to the presence of a bed of oozy 

 sand overlaid by a thick bed of clayey alluvium; the one being as import- 

 ant a cause as the other, but neither capable of producing the known 

 results without the intervention of the other. Vast, however, as these 

 effects appear, they are in reality insignificant, mere scratches in the paint 

 of the earth in whose history they will leave no permanent record. Hun- 

 dreds of acres of land may be broken up, thousands of tons of earth may 

 be precipitated into the river, and for days and. weeks, or even months, 

 the stream may boil and foam through the wreck, carrying ton after ton 

 of earth away in its turbid stream, but only to be deposited once more 

 lower down, or even in its ultimate destination, the sea. Time, however, 

 will put an end to all this disturbance; soon the river course will be cleared 

 and once more the river will flow as placidly as ever ; wind and rain will 

 break down the sharp edges of the overturned masses, will fill up the 

 cracks and holes, and in a few years at most the surface will be as 

 smooth and as luxuriantly clad with vegetation as ever it was before the 

 catastrophe. Indeed, so far from wondering at the wreck and ruin caused 

 by this earthquake, we should rather wonder that no traditions exist of 

 similar ruin produced by former earthquakes ; for we know that before 

 now earthquakes at least as violent have originated from the same 

 region ; and as the other determining cause, the existence of a soft 

 yielding bed, has always been present, it is wonderful that we should 

 have no record of such a striking phenomenon as would assuredly 

 have been exhibited. 



CHAPTER IV. 



THE POSITION AND EXTENT OF THE SEISMIC VERTICAL. 



The determination of the actual position of the seismic vertical, or 



that portion of the earth's surface over which the shock had a vertical 



emergence, is not in itself of great importance ; yet, as a knowledge of its 



position is necessary for the determination of the depth of the focus and 



( 60 ) 



