To give an idea of the efforts of a troubled sea against coasts, I shall relate a fact which has been affirmed to me by a creditable person, and which I the readier gave credit to, having seen something nearly similar. In the principal islands of the Orkneys there are coasts composed of rocks perpendicularly divided to the surface of the sea, to the height of near 200 feet. The tides in this place rise very considerable, as is common in all parts where there are projecting lands and islands; but when the wind is very strong, and the sea swells at the same time, the motion is so great, and the agitation so violent, that the water rises to the summit of these rocks, and falls again in the form of rain: it throws to this great height gravel and stones from the foot of the rocks, and some of them even broader than the hand. In the port of Livourne, where the sea is much more calm, I saw a tempest in December, 1731, wherein they were obliged to cut down the masts of some vessels that had been forced from their anchors by the wind, and driven into the road. The sea swelled above the fortifications, which were of a considerable height, and as I was on one of the most projecting works, I could not regain the town before I was wetted by the sea-water much more than I could have been by the most plentiful rain. These examples are sufficient to shew with what violence the sea acts against some coasts. This continual agitation destroys and diminishes by degrees the land. The water carries away all these matters, and deposits them as soon as it arrives at a part where the troubled sea subsides into a calm. In tempestuous weather the water is foul, from the mixture of matters detached from the shore and bottom of the sea, which then casts on the coasts a number of things that it brings from a distance, and which are never met with but after storms; as ambergris on the west of Ireland, and yellow amber on those of Pomerania, cocoa-nuts on the coasts of India, &c. and sometimes pumice and other singular stones. We can quote on this occasion a circumstance related in the new travels to the American Islands. "Being at St. Domingo, says the author, among other things they gave me some light stones, which the sea brought to the coast when there had been strong southerly winds; there was one two feet and a half long by eighteen broad, and one thick, which did not quite weigh five pounds: they are as white as snow, much harder than pumice, of a fine consistency, having no appearance of being porous, but when thrown into water, rebounded like a ball thrown on the ground, and it was with great difficulty they could be forced under the water with the hand." The stone must have been a very fine and close-grained pumice, which had issued from some volcano, and which the sea had conveyed, as it transports ambergris, cocoa-nuts, common pumice-stone, seeds of plants, rushes, &c. Observations of this kind have been generally made on the coasts of Ireland and Scotland.