Profeffor WiLLIAMS on Earthquakes. 285 
has been óbferved above. If this is the cafe, as I believe it is, 
future obfervations may determine it with much more certainty 
and precifion, than any that have yet been made. 
But although we are able to difcern fome appearances of agree- 
ment and fimilitude in thofe phenomena that have been menti- 
ened, we cannot difcern any in the times in which thefe earth- 
quakes have happened. From their having i all proceeded in 
the fame courfe, one might be led to fufpe&t, whether their 
caufes, whatever they are, operating in the fame direction, 
would not require nearly the fame intervals of time, to gather 
failicient force to produce the fame effects. . But nothing of 
this nature is apparent. The intervals of time, at which they 
have happened, have been very different, and without any ap- 
parent regularity. Not to mention the fmaller (hocks, there 
have been five which have been diftinguifhed by their being 
much larger than the reft: thofe, I mean, of 1638, 1658, 1663, 
1727 and 1755. Between the two former of thefe, there was 
án interval of twenty-eight years. —Between the two next, an in- 
terval of five years: then one of fixty-four ; and between the 
two Jatt, of twenty years. Ata medium, this will make one 
in about twenty: feven years. But in thee different intervals, 
flere is no ‘Apparent order, regularity, or proportion, in Hé 
&mes-of their happening. Neither does there feem to be any 
proportion between. the intervals of time, and the violence of the 
frock. One would be apt to imagine, that the longer the 
 €aufes were gathering ftrength, the greater would be the vio- 
ncs caa when it came : and yet that of 1755 
was greater than that of 1727, though the interval of time had 
not been half fo long. It isto be obferved, however,. that as 
ar accounts of the earthquakes are but impesfect, as to their 
number, 
