134 Geological Society. 
tula Northiana. Caulis brevis simplex, foliis erecto-patentibus, 
lineari-lanceolatis, acutis, siccitate tortuosis, theca subcylin- 
drica (named after LordGuildford.)—Bryum elegans.—B. Don- 
ianum.—Hypnum Leskea. 
Feb. 21.—The Reading of Dr. F. Hamilton’s Commentary 
on the Hortus Malabaricus, Part IV., was begun. 
GEOLOGICAL SOCIETY. 
Jan. 20.—A paper was read On the Geology of Jamaica, 
by H. T. Dela Beche, Esq., F.R.S. &c. 
Mr. De la Beche’s observations are confined to the eastern 
half of Jamaica, which includes the whole range of the Blue 
Mountains, the highest eminences of the island, those of Port- 
Royal, Spanish-Town, the Mocko Mountains, and other ridges 
of inferior elevation. These heights often mclude or are con- 
nected with extensive plains, the principal of which are those 
of Liguanea, Vere, and Lower Clarendon, Luidas Vale, and 
St. Thomas’s. The rocks of oldest formation which presented 
themselves to the author, within this district, he refers to the 
submedial or transition series. They compose the greater 
part of the Blue Mountain range, and consist of, 1. Gray-wacke, 
both foliated and compact, coarse and fine; presenting in short 
the usual variations common to this rock in Europe, and ap- 
pearing, on some points, to pass into old red sandstone: 2. 
Transition limestone, apparently destitute of organic remains, 
compact, of a dark blueish gray colour, and traversed by veins 
of calcareous spar; occasionally associated with argillaceous 
slate, and its upper beds much intermixed with sandstones. 
These stratified rocks throughout the Blue Mountains gene- 
rally dip towards the N.E. and E.N.E. at a considerable angle ; 
but there are frequent exceptions to this rule, and the strata 
are on the whole much contorted. They are occasionally as- 
sociated with trap rocks, viz. syenites, greenstones, and clay- 
stone porphyry. The author observed on one point, viz. the 
southern slope of St. Catherine’s hill, a series of strata which 
he conceives to represent the coal measures; the old red 
sandstone is however developed on a larger scale, and in more 
numerous localities: so that the medial or carboniferous series 
is certainly not wanting in Jamaica. Resting upon this ap- 
pears, on many points, a porphyritic conglomerate, associated 
with porphyry, and occasionally with greenstone and syenite. 
Similar trap rocks, intermixed in the most varied manner, 
show themselves very extensively, composing the greater part 
of the St. John’s Mountains, and the district bordering on the 
Agua Alta. One variety of porphyry met with by the author 
is composed of nodular coneretions, separated by a a argil- 
aceous 
