HILL: GEOLOGY OF JAMAICA. 97 
land Ridge of Clarendon, which constitutes the southern peninsula of 
the island, and at another by the extensive outliers of the Limestone 
Plateau known as the Healthshire and Port Henderson Hills, opposite 
the Naval Station of Port Royal. The latter are conspicuous features 
to the west as one enters Kingston Harbor. The Braziletto Hills of 
Clarendon extend into this plain, almost separating it into eastern and 
Western divisions. The term Liguanea is restricted in local usage to 
that portion of the plain lying east of this prolongation. The interior 
margin of the plain terminates against the steep white limestone topog- 
raphy, except just north of Kingston, where it abuts against the Blue 
Mountain ridges proper. This interior margin is over 800 feet high 
Hear Constant Springs, whence it slopes rapidly to the sea at Kingston, 
six and a half miles distant. 
In comparison with regions underlain by other formations, the physieal 
aspect of this plain is arid and sterile. | The flora, including thorny 
Acacias and cactus, tends towards the chapparal type so character- 
istic of the Rio Grande Plain of Mexico and Texas, and presents a 
Striking contrast to the deciduous tropical flora of the remainder of 
the island. To the west the next extensive plain of this character, 
known as the Pedro Plain in St. Elizabeth, indents the land to the 
east and north of Black River Bay. Its estimated area is over 100 
"quare miles. This is analogous to the Plain of Liguanea, except 
that it contains much marshy ground, and the gravel formation is accom- 
panied by marls. Back of Savanna-la-Mar there is another extensive 
plain of this type, whieh continues inward nearly one half the dis- 
tance across the island. This is cut entirely out of the limestone hills, 
aud, inasmuch as there is little gravel in the back country, the formation 
is ofa marly nature, This plain is fully 100 square miles in area. On 
the west it is almost connected by a narrow arm with the marshes which 
border the western coast of the island. Plains of this character are sin- 
Sularly absent from the north side except at Montego Bay adjacent to 
the mouth of Montego River, where they are more feebly developed than 
on the south coast. 
The history of the Liguanea type of Plains is a record of four dis- 
tinct events : (1) the original cutting out of the topographic matrix 
during an antecedent period of base levelling ; (2) the filling in of 
the débris which composes the present surface material of the plains ; 
(3) the elevation of the plains into their present position above the sea; 
and (4) the cutting of the modern streamways across them. The sur- 
face formation of those plains is clearly deposited in pre-eroded valleys 
