338 Conjectures concerning the Cause, and Observations 
98, In computing the times in the preceding table, allowance 
was made for the difference of longitude, as it is laid down in the 
common maps, which are not always greatly to be depended 
on. The times themselves also are often so carelessly observed, 
as wel! as vaguely related, that they are many of them subject to 
considerable errors; the concurrent testimonies, however, are so 
many, that there can be no doubt about the main point; and, 
that the errors might be as small as possible, I have not only en- 
deavoured to select those accounts that had the greatest appear- 
ance of accuracy, but, in all cases where it was to be had, | have 
always taken a mean amongst them. In many of the accounts, 
the relaters say only between such hours, or about such an hour : 
of this kind were the accounts of the times of the agitation of 
the waters at the Hague and Lochness, which vary the most from 
a medium of the rest, the former erring about seven minutes in 
defect, and the latter about twenty minutes in excess: with re- 
gard to the latter, however, I must observe, that, from the ac- 
count itself, it is probable the agitation happened sooner than 
eleven o’clock, which is the time mentioned. The accounts also 
of the time of the agitation of the waters in the northern parts 
of England, seem to confirm the same thing*. 
99. It is observable, in the preceding table, that the times, 
which the wave took up in travelling, are not in the same pro- 
portion with the distances of the respective places from the sup- 
posed source of the motion: this, however, is no objection against 
the point assumed, since it is manifest, wherever it was, that it 
could not be far from Lisbon, as well because the wave arrived 
there so very soon after the earthquake, as because it was so 
great, rising, as we are told, at the distance of three miles from 
Lisbon, to the height of fifty or sixty feet. The true reason of 
this disproportion seems to be the difference in the depth of the 
water ; for, in every instance in the above table, the time will be 
found to be proportionably shorter or longer, as the water through 
actly, might have served, perhaps, to ascertain the distance of those two 
places from the original source a little more accurately; but, as the distance 
of neither from thence could be very great, a small difference in them would 
hardly sensibly affect any of the others ; from which, therefore, we may 
draw the same general conclusions, as if thev were exact. 
* As the shortest way that the vapour could pass from near Lisbon to 
Lochness was under the ocean, possibly it might, on that account, be some- 
what retarded ; for the water adding to the weight of the superincumbent 
mass, and not to its elasticity, must } produce this effect in some degree: it 
is probable, however, that this could make no great difference, as the motion 
seems to have been very little retarded in its passage from the original 
source to Madeira, to which place, I suppose, it must have passed under 
deeper seas than would be found in its road to Scotland. 
which 
