THE earthquake at Lisbon, which you gave me an account of, was certainly the most awful tremendous calamity, that has ever happened in the world. Its effects are extremely wonderful and amazing; and it seems, as you observe, to have been felt in all parts of the globe. On the 3d day of the same month the earthquake of Lisbon happened, I felt at Manna[1] a violent shock myself; and from that time to the 3d of December following I felt no less than twelve different shocks, all which I took an exact account of in my pocket-bock. Since which we have had two very severe earthquakes, felt, we believe, throughout this island[2]. The walls of[3] Cumberland-house[4] were greatly damaged by them. Salop-house[4], my own (formerly Mr. Massey’s), the houses of Laye[5] and Manna, were all cracked by them; and the works at the sugar-plantation[6] received considerable damage. The ground opened near the _qualloe_[7] at Bencoolen, and up the River in several places; and there issued therefrom sulphureous earth, and large quantities of water, sending forth a most intolerable stench. Poblo Point[8] was much cracked at the same time; and some _doosoons_[9] in-land at Manna were destroyed, and many people in them. These are all the ill effects, that have come to our knowlege; but, it is reasonable to suppose, not all the damage, that has happened upon the island. LXIII. _Concerning the Fall of Water under Bridges. By Mr._ J. Robertson, _F.R.S._ [Read Jan. 19, 1758.] SOME time before the year 1740, the problem about the fall of water, occasioned by the piers of bridges built across a river, was much talked of at London, on account of the fall that it was supposed would be at the new bridge to be built at Westminster. In Mr. Hawksmore’s and Mr. Labelye’s pamphlets, the former published in 1736, and the latter in 1739, the result of Mr. Labelye’s computations was given: but neither the investigation of the problem, nor any rules, were at that time exhibited to the public.