Gentil, in his voyage round the world, speaks of earthquakes in the following terms: "I have, says he, made some remarks on these earthquakes; first, that half an hour before the earth is agitated every animal is struck with fear; horses snort, break their fastenings, and fly from the stable; dogs bark; birds, as if stupified, fly into houses for safety; and rats and mice quit their holes. Secondly, that vessels at anchor are so violently agitated, that every part of them seems as if going to pieces, the cannons force themselves loose, and the masts break in several places. These facts I should scarcely have given credit to if many unanimous testimonies had not convinced me. I know the bottom of the sea is a continuation of the land, and that if one is agitated it will communicate to the other; but I could not conceive how every part of a vessel, floating in a fluid, should be affected in the same manner as if she was on the earth: it appeared to me that her motion should have been such as she experiences in a storm; besides, in the circumstance which I speak of, the surface of the sea was smooth, and there was no wind. Thirdly, that if the cavern of the earth, where this subterraneous fire is contained, has a direction from north to south, and if the buildings of an adjacent town are in a parallel line with it, all the houses are overthrown, whereas if this vein or cavern executes its effects by the breadth of the town, the devastation of the earthquake, is much less considerable."[Y] [Y] See Gentil's Voyages, vol. I. page 172, &c. In countries subject to earthquakes, when a new volcano breaks out earthquakes cease, and are only felt in the violent eruptions of the volcano, as is observed in the island of St. Christopher.[Z] [Z] See Abridgement of Phil. Trans. vol. XI. page 302.