17t)9. ROUND THE WORLD. 175 



been the bed of the sea, and thrown up in heaps, to 

 a height which the waters never reach. One or other 

 of these suppositions will perhaps be thought the 

 more probable, as the water does not gradually grow 

 shallow as the shore is approached, and the islands 

 are almost every where surrounded by reefs, which 

 appear to be rude and broken, as some violent con- 

 cussion would naturally leave the solid substance of 

 the earth. It may also be remarked upon this oc- 

 casion, that the most probable cause of earthquakes 

 seems to be the sudden rushing in of water upon some 

 vast mass of subterraneous fire, by the instantaneous 

 rarefaction of which into vapour the mine is sprung, 

 and various substances, in all stages of vitrification, 

 with shells, and other marine productions, that are 

 now found fossil, and the strata that covered the 

 furnace, are thrown up ; while those parts of the land 

 which were supported upon the broken shell give 

 way, and sink into the gulf. With this theory the 

 phaenomena of all earthquakes seem to agree : pools 

 of water are frequently left where land has subsided ; 

 and various substances, which manifestly appear to 

 have suffered by the action of fire, are thrown up. 

 It is indeed true, that fire cannot subsist without air ; 

 but this cannot be urged against there being fire 

 below that part of the earth which forms the bed of 

 the sea ; because there may be innumerable fissures 

 by which a communication between those parts and 

 the external air may be kept up, even upon the highest 

 mountains, and at the greatest distance from the sea- 

 shore. 



On the 4th, Mr. Banks employed himself in plant- 

 ing a great quantity of the seeds of water melons, 

 oranges, lemons, limes, and other plants and trees 

 which he had collected at Rio de Janeiro. For 

 these he prepared ground on each side of the fort, 

 with as many varieties of soil as he could choose 5 and 

 there is little doubt but that they will succeed. He 



