458 PHILOSOPHICAL TRANSACTIONS. [aNNO l/GO. 



thrown from the volcano Cotopaxi, by one of these blasts, to the distance of 

 more than 3 leagues. 



If we suppose that these vapours, when pent up, are the cause of earthquakes, 

 we must naturally expect that the most extensive earthquakes should take their 

 rise from the level and low countries ; but more especially from the sea, which is 

 nothing else than waters covering such countries. Accordingly we find that the 

 great earthquake of Nov. 1, 1755, which was felt at places near 3000 miles 

 distant from each other, took its rise from under the sea ; as is manifest from 

 that wave* which accompanied it. The same thing is to be understood of the 

 earthquake that destroyed Lima in the year 1746, which, it has been said, was 

 felt as far as Jamaica; and as it was more violent than the Lisbon earthquake, 

 so if this be true, it must probably have been more extensive also. There have 

 been many other very extensive earthquakes in South America : Acosta says 

 that they have been often known to extend themselves 1 , 2, or 300, and some 

 even 500 leagues along the coast. These have been generally, if not always, 

 attended with waves from the sea. 



Sect. 3. Mr. M. having said before, that he imagined earthquakes were caused 

 by vapours raised from waters suddenly let out upon subterraneous fires, does 

 not easily find any other cause capable of producing such sudden and violent 

 effects, or of raising such an amazing quantity of vapour in so small a time. 

 That the blasts discharged from volcanos are always produced from this cause is 

 highly probable; that they are often so cannot admit of the least doubt. There 

 can be no doubt, that considerable quantities of water must be often let out upon 

 the fires of these volcanos, and whenever this happens it will be immediately 

 raised by their heat into a vapour, whose elastic force is capable of producing 

 the most violent effects.* 



* There are many effects produced by the vapour of water, when intensely heated, which make 

 it probable, that the force of gunpowder is not near equal to it. The effects of an exceedingly small 

 quantity of water, on which melted metals are accidentally poured, are such as could in no wise be 

 expected from the like quantity of gunpowder. Founders, if they are not careful, often experience 

 these effects to their cost. An accident of this kind happened about 40 years since, at the casting 

 of C brass cannon at Windmill-hill, Moorfields. ' The beat of the metal of the first gun drove so 

 much damp into the mould of the second, which was near it, that as soon as the metal was let into 

 it, it blew up with the greatest violence, tearing up the ground some feet deep, breaking down the 

 furnace, untiling the house, killing many spectators on the spot with the streams of melted metal, 

 and scalding many others in a most miserable manner.' [See the note at the end of process 44th of 

 the English translation of Cramer's Art of Assaying Metals. 



Other instances of the violence of vapours raised from water are frequently to be met with: one 

 of Papin's digesters being placed between the bars of a grate, where there was a fire, was after some 

 time burst by the violence of the steam, the fire was all blown out of the grate, and a piece of the 

 digester was driven against the leaf of a strong oak table, which it broke to pieces. [See Phil. 



