194 Conjectures concerning the Cause, eo. of Earthquakes. 
33. From these instances, we may, with great probability, 
conclude, that the fires of volcanos produce earthquakes : I do 
not, however, suppose, that the earthquakes, which are frequently _ 
felt in the neighbourhood of volcanos, are owing to the fires of 
those volcanos theinselves; for volcanos, giving passage to the ~ 
vapours that are there formed, should rather prevent them, as in 
the instance at St. Ciiristopher’s, before mentioned. 
34, We also meet with frequent instances confirming the same 
thing amongst the Andes. Antonio d’Ulloa (speaking of what 
happens amongst these mountains) says, “‘ Experience shows us, 
that, upon the fresh breaking out of any volcano, it occasions so ~ 
violent a shock to the eafth, that all tie villages which are near 
it are overthrown and destroyed, as it happened in the ease of 
the mountain Carguayraso*. This shock, which we may, without 
the least impropriety, call an earthquake, is seldom feund to acs 
company the eruptions, after an opening is once made; or, if 
some small trembling is perceived, it is very ineonsiderable; so 
that, after the volcano has once found a vent, the shocks cease, 
notwithstanding the matter of it continues to be on fire.” The 
greater earthquakes, therefore, seem rather to be occasioned by 
other fires, that lie deeper in the same tract of country; and the 
eruptions of voleanos, which happen at the same time with earth- 
quakes, may, with more probability, be ascribed to those earth- 
quakes, than the earthquakes to the eruptions—whenever, at _ 
least, the earthquakes are of any considerable extent. If this don’t 
appear sufficiently manifest at present, it will, perhaps, be better 
understood, by applying to the present purpose, what will be said 
‘hereafter concerning local earthquakes. 
Section II].—39. It may be asked, perhaps, why we should 
suppose, that several subterraneous fires exist in the neighbour- 
hood of volcanos? In evidence of this, we have frequent in- 
stances of new volcanos breaking out in the neighbourhood of old 
ones: Carguayraso, just mentioned, may supply us with one ex- 
ample to this purpose ; atid in the night of the 28th of October 
* [t does not appear altogether certain, from the expression made use 
of in the French translation (from whence I have taken this), that Car- 
guayraso might not have been a volcano in former times, which is asserted 
to have been the case by Mous. Coudamine. It is possible also, that the 
satne may be true of those four mentioned in the next article; arid, indeed, 
it is difficuit to know it io be otherwise, in any instance, among the Andes, 
where. the volcanos are generally found at inaccessible heights. But al- 
lowing that all these were only old volcanos, which broke out afresh, yet 
they will serve at least to swell the number of them in the same neighbour- 
hood, as well as to show us, that there may, very probably, be many more, 
wSich lie hid: for these showed no marks of their existence, till, by their 
eruption, they melted a vast quantity of snow, with which they were be- 
fore covered, and which, being reduced to water, did great damage, by 
overflowing the country round about, ; inet 
1746, 
