1825.} the Diluvium of' Janlgdca, 



The. alcove septipn^wj^V^xpljtin better th^n, .W9rds the manner 

 in which the diluvium '(A) abuts againstthe Si. !^'n^rew'^^ 

 tains.(B). The latter are composed of porphyry, syemte, greei?i' 

 stone, brownisli red pprphyritic conglomerate, siliceous sand- 

 stones, shales, and coal, that resemble our coal measures, with 

 red sandstones and conglomerates of an older date resting upofii^ 

 transition rocks. Rounded portions of all these rocks compose' 

 the gravel of Liguanea ; the pebbles are not in geneml very^ 

 large ; blocks, however, of siliceous sandstone, and of (jonsidet- 

 able dimensions, are found near the Hope estate, the property 

 of the Duke of Buckingham. '- ' ^ *^ -^*^ jii.u. J 



The Hope river, with the Mammee river- which falls into it, 

 drains a considerable portion of the St, Andrew's mountains, and, 

 when the waters are low, loses itself among the Liguanea 

 gravels, at that part of its course where first quitting the rocky 

 defiles of the mountains it enters upon this diluvial plain ;but 

 when the river is swollen by heavy tropical rains, it becomes a 

 torrent of considerable magnitude, rushing with great force 

 through the defile which opens upon the plain, by the continual 

 recurrence of which it has excavated the gravel to a considerable 

 depth ; so that in fact the causes now in action tend to destroy 

 the gravel plain rather than form it. The section of diluvial 

 gravel made by the river near the Hope Tavern, cannot be less 

 than between 3G0 and 400 in depth, and the tavern itself is, 

 according to the barometrical measurement I made, 698 feet 

 above the level of the sea. The diluvial gravel rises some 

 height above the tavepi. A 



Proceeding up the Hope Valley, a part of the road displays a 

 section of diluvium (the rounded rock pieces of which are large), 

 resting upon a projecting portion of the mountain that rises 

 about 600 feet above the bed of the river. 



In addition to the Hope river, numerous gullies formed by 

 heavy tropical rains, cut the diluvial plain of Liguanea in various 

 directions, so that far from being formed by the waters which 

 now descend from the mountains, every stream that traverses it 

 tends to destroy it, and carry the gravel into the sea. . » 



This plain descending gradually to the sea, and being pro- 

 tected from the ravages of the latter by the Palisades, a sand 

 bank extending several miles from Port Royal to the main land, 

 alluvial matter is deposited on parts of the shore, more particu- 

 larly between Kingston and Port Henderson, on which mangrove 

 trees are numerous ; in fact these trees are extremely well calcu- 

 lated for the accumulation of alluvium, their long stilt-like roots 

 collecting mud and other matters together, and then protecting 

 what they have collected from being washed away by any 

 violent rush of water, the numerous roots breaking its force. 



It is almost impossible to stand upon the gravel p|ai|J^^f Ligua- 

 nea without feeling convinced that it could not ""have been 



