184 Mr. De la Beche on the Geology of Jamaica. 



between Kingston and Port Henderson, where mangrove trees are numerous. 

 These trees are particularly well calculated for the formation of alluvium, their 

 long stilt-like roots collecting mud and other matters together, and protect- 

 ing what they have accumulated from any sudden rush of water. 



The diluvial plain of Liguanea is continued westward through the lowlands 

 of St. Catherine's and St. Dorothy's ; sands and clays are more abundant in 

 these districts, but in other respects the diluvium is the same. The sections 

 afforded by the rivers and gullies are of considerable interest, though there is 

 no one so deep as that of the Hope River. 



Bones of the elephant, rhinoceros, &c. have certainly not yet been dis- 

 covered in the Jamaica gravels : but it should be recollected that the oppor- 

 tunities for such discoveries are by no means so common as in those countries 

 where gravel is extensively used for roads, &c. The climate, moreover, is 

 such that few feel tempted to risk their health by prosecuting researclies of 

 this nature. The large plain of Vere and Lower Clarendon is separated from 

 the above by the low range of white limestone hills formerly mentioned. It 

 is surrounded by white limestone hills and mountains on all sides save on the 

 south and south-east, where it is washed by the sea, with the exception of that 

 portion protected by Portland Ridge. The greater part of this plain is dilu- 

 vial, consisting of gravels, clays, and sands; the former are principally com- 

 posed of porphyry, greenstone, and other trap rock pebbles, that would appear 

 to have been in a great measure derived from the partial destruction of the 

 trap districts among the St. John's and Clarendon mountains. 



Many good sections are afforded of this diluvium by the Rio Minho, which 

 traverses it nearly through its whole length, as also by many deep gullies ; it 

 is easy to remark here, as in Liguanea, that the causes now in action tend to 

 destroy this plain, and are altogether inadequate to its formation. 



It is remarkable, that, though the diluvium of this district is nearly sur- 

 rounded by white limestone hills and mountains, very few fragments of this 

 rock are found in it ; from which circumstance it would appear that the lime- 

 stones, though in general tolerably compact, were unable to resist the effects 

 of violent attrition so well as the greenstones, porphyries, &c. The Vere and 

 Clarendon diluvium rests for some distance upon the Savannah sandstones 

 and conglomerates before mentioned, and it is often very difficult to distin- 

 guish between them. 



Diluvium occurs at the bottom of Luidas Vale, and in some parts of St. 

 Thomas-in-the-Vale ; and, mixed with alluvium, it forms a considerable tract 

 of low land between Annotto and Buff" bays. As might be expected the 

 mouths of the rivers are alluvial, but some of the country about Welsh Wo- 



I 



