400 . Profefar WinriAMs on Earthquakes. 
fulphureous mixtures that have been thrown out at the different 
eruptions. Inftances of thefe eruptions are mentioned in the 
accounts of the earthquakes of 1727 and 1755.—And they are 
fuch as make it probable, that there is fome particular fratum 
under the furface of the country, which has ferved and will 
ferve to dire& the motion of the fubterrancous vapour, from 
: the places of its origin, to that of its grand final eruption.* 
On this account of the Caufes of the Earthquakes of New- 
England, it may not be amifs to remark, that part of it feems 
to be matter of /27, and part matter of conjecture. As the 
caufes lie out of fight, and beyond the reach of obfervation, we 
have no way to come to the knowledge of them, but by gene- 
ral reafonings from the phenomena that fall under our obíerva- 
tion. Thefe phenomena, I may venture to fay, have been fair- 
ly related :—but whether the inferences that have been drawn 
from them, are juft,—the conjectures, fuch as.are probable,— 
ate conclufions, well Spee —and the evidence, fuch as 
* might 
7* Such ds not at all uncommon. Many countries are known to abound 
with, and to be-diftinguifhed by them. ‘ We have an inftance of it in the chalky 
and flinty countries of England and France, which (excepting the interruption of 
the channel, and the clays, fands, &c. of a few counties) compofe a traé of 
about three hundred miles each way.” Phil. Tranf. for 1760, p. 587. The vol- 
canoes in the Andes, are in all probability derived from the fame fratum of com- 
. bufüble minerals ; the extent of which cannot be lefs than five thoufand miles, —for 
fo far do the mountains and volcanoes extend. —And thus in North-America, if we 
: "may give credit to L. Evans, in defcending from the mountains which adjoin to 
3 ers ehe — the fame fets of frata, and in the fame order, are generally 
ikto countries, earthquakes have ceafed upon P breaking out of volcanoes. 
1 Vere icd volcanoes i in this part of America, which might ferve to interrupt the 
frratum, and as a = for the fubterraneous vapours to difcharge themfelves, it is 
» probable the earth es:of New-L£ngland would not run in fuch a regular manner, 
through: fach an exte of the country, 
* 
