156 ON THE REVOLUTIONS 



I have made a few experiments lately with explosions of 

 some pounds of gunpowder under water, in order to try the 

 effect of sudden impulse. In every case, a very manifest heave 

 of the surface was produced at the instant of the explosion ; 

 and at that same instant, a very smart percussion was felt. 

 This was always followed in two or three seconds by a distinct 

 and separate agitation of the water, occasioned by the rising 

 of the permanently elastic gases produced in the explosion. 

 The form given to the wave in fig. 1. has been sketched from 

 the recollection of that first momentary impulse. 



We have thus a theory of those waves which seem almost in- 

 variably to have accompanied the great earthquakes ; supposing 

 these to have been occasioned by submarine elevations, and to 

 form an intermediate step between the Volcanic eruptions, and 

 the truly Plutonic operations by which our continents have been 

 elevated. 



But, to return to the alpine scenes with which we set out : 

 If the phenomena on the banks of the lake of Geneva, to 

 which we have alluded, were really occasioned by a torrent of 

 water, its magnitude must have been such as to leave few ve- 

 stiges of the human race, in Europe at least, to record the cir- 

 cumstance ; and we can only expect to find proofs of its reality 

 in geological facts. The events of Lisbon and of Callao, 

 though on a scale comparatively diminutive, help to lead 

 our imagination to the conception of this colossal disaster. 

 It may still, however, be alleged, as I have already hinted, 

 that it would be impossible for water of any depth whatever, 

 or moving with any velocity, to carry blocks of such magnitude 

 to such situations ; and the consideration is of so great import- 

 ance, that I am induced, in attempting to unite the ideas of 

 Saussure with those of Hutton, to retain part of the system 



proposed 



