ABOUT VOLCANOS AND EARTHQUAKES. 17 



often several yards. In the earthquake of Cutch, which 

 I have mentioned, trees were seen to flog the ground 

 with their branches, which proves that their stems must 

 have been jerked suddenly away for some considerable 

 distance and as suddenly pushed back; and the same 

 conclusion follows from the sudden rise of the water of 

 lakes on the side where the shock reaches them, and its 

 fall on the opposite side ; the bed of the lake has been 

 jerked away for a certain distance from under the water 

 and pulled back. 



(24.) Now, suppose a row of sixty persons, standing 

 a mile apart from each other, in a straight line, in the 

 direction in which the shock travels ; at a rate, we will 

 suppose, of sixty miles per minute : and let the ground 

 below the first get a sudden and violent shove, carrying 

 it a yard in the direction of the next. Since this shock 

 will not reach the next till after the lapse of one second 

 of time, it is clear that the space between the two will be 

 shortened by a yard, and the ground that is to say, not 

 the mere loose soil on the surface, but the whole mass of 

 solid rock below, down to an unknown depth com- 

 pressed, or driven into a smaller space. It is this com- 

 pression that carries the shock forwards. The elastic 

 force of the rocky matter, like a coiled spring acts both 

 ways ; it drives back the first man to his old place, and 

 shoves the second a yard nearer to the third ; and so on. 

 Instead of men place a row of tall buildings, or columns, 

 and they will tumble down in succession, tl^e base flying 

 forwards, and leaving the tops behind to drop on the 

 soil on the side from which the shock came. This is 



B 



