1897-98]- LATE FORMATIONS AND GREAT CHANGES OF LEVEL IN JAMAICA. 35I 



canyons^ such as those along the streams shown in Map, Figure 4. 

 Above the canyon sections, there are benches marking the former floors 

 of the valleys, before the post-Liguanea uplift (as represented by the 

 base levels shown in section at 1.1., Figures 5 and 7, and z in Figure 



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Terraces. — Remnants of terraces are common, but they are usually 

 very much denuded by the tropical rains which may amount to ten 

 inches fall within twenty-four hours. It is almost astonishing that any 

 loams and gravels resist such washes. Under these conditions the 

 torrents rise to great heights in the gorges, so that large boulders 

 commonly five feet and occasionally ten feet in diameter are carried 

 down the channels for many miles from their original beds. 



Back of Kingston the Liguanea plain rises 350 feet in three and 

 a-half miles, and near Hope Toll Gate to about 600 feet ; but this is 

 upon the edge of the delta of the Hope River, where it leaves the 

 mountains. A short distance away, on the Mono estate, there is a 

 beautiful terrace plain at 550 feet (bar.), and lower terraces at 500 and 

 460 feet. Below this level the river enters the canyon. These are true 

 terrace steps, each marking the lowering of the base level of the erosion 

 of the river. Through the canyon, which is more recent, there is no 

 terrace, but at the lower end where it expands to a broad valley, another 

 terrace at 150 feet is seen. The floor of the valley is here 100 feet 

 above tide, but the bottom merges into lateral terraces of about the 

 same height along the lower reaches. Other terraces at 50 and 25 feet 

 also occur. 



Terraces, corresponding to those of the broader parts of the Hope 

 River valley, ought to be engraved upon the Liguanea plain, but they 

 are only faintly recorded. These open plains which have been ex- 

 posed not only to the tropical rains, but to the cultivation of 350 

 years, would naturally have the faces of the terraces, of which only the 

 more striking have been noted along the Hope, graded down to a some- 

 what uniform slope ; but even now some of these steps are still 

 recognizable. On the southern end of Long Mountain, there is a 

 bench cut in the White Limestone at an elevation of about 550 feet, 

 corresponding in height to the Mono Terrace (at 1 1., Figure 5, page 344). 



Along the line of the railway, west of Old Harbour, terraces of 

 gravel, etc., were noticed at 275, 250, and 175 feet, and beyond Porus 

 Station at 400 feet. Still farther, the Melrose valley appears to be a 

 terrace floor protected in a cove among the mountains. In St. 

 Thomas-in-the-Vale, back of Spanish Town, terraces are well shown at 



