1911.] 



NATURAL SCIENCES OF PHILADELPHIA. 



121 



liamsfield and Poms are located, at an elevation of some 1,000 feet 

 lower than that of Mandeville. The country has been settled for 

 many years; in some places but little original forest remains, in 

 others, especially to the north, northwest, west and southwest of the 

 town, large tracts are still covered by original forest. The under- 

 lying rock is the Tertiary limestone which forms the surface of Jamaica 

 outside of the great uplift of the Blue Mountain system and belongs 

 mostly to the Cobre formation of Hill. These limestones are generally 

 nearly horizontal or only gently inclined, they outcrop on steep slopes 



Kendal 



VV^mV"! sfirlri 



Fig. 1. — Sketch map of the Mandeville region. 



of the hills and many hill-tops and stand up in long cliffs on the hill- 

 sides. There is no surface water in the district, but the limestones 

 are eaten out into caverns and the drainage is underground. Some 

 of the limestone layers are very pure, some are quite marly. The 

 weathering of the rock depends upon these characters and the two 

 types of stone mentioned present quite different structures when they 

 weather. The marly limestone shows but little in the way of corals 

 or shells or other fossils, being rather even in grain and evidently 



