HILL: GEOLOGY OF JAMAICA, or 
To the ordinary traveller this back coast topography is principally 
interesting from its scenic features. To the topographer it reveals a 
Series of most interesting ancient terrace levels, which give important 
testimony concerning the history of the island. Some of these are 
beautifully shown on the east side of Montego Bay (see Plate XX.), 
Where six distinct levels or benches separated by deep slopes rise above 
the sea in stair-like arrangement. At no other single locality are so 
many of these levels shown in such close juxtaposition but one or more 
9f them can bo individually distinguished at many localities entirely 
around the island, as well as some others as high as 2,000 feet. Ata 
singlo glance these terraces in Jamaica do not present the perfection of 
the allied phenomena exhibited on the southeast coast of Cuba, but 
nevertheless, they record a similar geological history. 
Naturally tho integrity of these levels varies with their relative age 
and altitude. Those of higher altitudes are more fragmentary because 
degradational processes have been working upon them longer. Frag- 
ments of the lower benches are better preserved, although much broken 
by erosion, while none of them are as perfect in contour as the benches 
of the Coastal Plain. All have been cut across by rivers, etched and 
dissolved by rainfall, and undermined by encroachment of the waves, so 
that they are now often indistinct, but there are sufficient remnants in 
Jamaica to enable tho student of geomorphology to recognize them. 
Without an accurate topographie survey of the island, it is impossible 
to correlate correctly all the different benches or to do more than approxi- 
Mate their altitudes. The following general statements concerning them 
are based upon personal observations. The high sky line of the back 
Coast border, as seen from the sea, in some cases represents the survival 
of the oldest summit topography of the plateau, and in others benches 
and terraces which have been successively cut out of it during inter- 
Mittent periods of elevation. The highest of the old benches is John 
Crow Ridge, a long narrow shoulder which is seen in approaching the 
island from tho Windward Passage ; it projects seaward from the Blue 
Mountains and extends from back of Northeast Point near Port Antonio 
Southeast to Holland Bay. It may be a remnant of the summit topog- 
raphy of the old plateau level. It is apparently a continuous hori- 
zontal plateau composed of several patches of level surface, ending to 
the southeast with the area known as the “ Big Level.” The interior 
or landward side of the John Crow Plateau is now separated from the 
"ug Mountain Ridge by the tremendous ravine of the Rio Grande. 
10 higher summit of Yallahs Mountain on the south coast (see Plate 
