SECTIONAL TRANSACTIONS.—C, 391 
On the whole, the Pre-Cambrian formations indicate cooler conditious than 
the Palwozoic up to the end of the Carboniferous, and much cooler conditions 
than those of the Mesozoic. 
Wednesday, August 13. 
22. Mr. Epwarp M. Kinpir.—Certain Types of Sedimentation now 
in Progress on or near the Atlantic Coast of North America. 
Certain phases of sedimentation on the Labrador coast, the Bay of Fundy, 
the south-east coast of Florida, and the Bahama islands are briefly described. 
These include the current-formed terraces of Lake Melville, Labrador, and 
other features relating to the inland and sea coast sediments of Labrador, the 
deposits of the inter-tidal zone of the Bay of Fundy, the Coquina beds of St. 
Augustine, Florida, and the exolian limestone of Providence Island in the 
Bahamas. Examples of lithification of calcareous deposits now in progress in 
the Florida-Bahama region are described. ‘ 
23. Dr. C. A. Martry.—Recent Geological’ Work in Jamaica. 
The paper gives a preliminary account of the scientific results obtained in 
the course of geological investigations of an economic character, chiefly in con- 
nection with water-supply, in various parts of Jamaica. The author was 
assisted in the later stages of the work by Mr. G. M. Stockley, A.R.C.S., 
A.I.C., F.G.8., and he is indebted to Dr. T. W. Vaughan and Dr. W. P. 
Woodring, of the U.S. Geological Survey, for the examination of some of the 
foraminifera and mollusca of the White Limestone. 
The field work confirms in its main outlines the mapping of the formations 
by Sawkins and his colleagues as shown on their map of 1865, with the exception 
of the unfortunate mistake, afterwards corrected by Prof, Hill, of correlating 
with the Yellow Limestone certain strata in the east of the island which are 
newer than the White Limestone. Several other corrections introduced by Hill 
in his revision of Sawkins’s map (1899) are, however, not accepted. The strata 
are capable of greater subdivision than has been previously recognised or 
attempted, the subdivisions of the older rocks being chiefly lithological, and of 
the newer rocks chiefly paleontological. 
The Metamorphosed Series of ,Sawkins, as Hill has pointed out, is not a 
stratigraphical series. In the mountainous country to the north-east of 
Kingston it is a folded complex of rocks, of which the dominant member is a 
great mass, apparently not less than 1,000 feet thick, of pale buff or grey 
porphyry, with phenocrysts of hornblende and felspar and sometimes of quartz, 
which was intruded as a laccolite or sill before, or at an early stage of, the 
‘folding. It has already been traced over a belt of country, with a N.W.-S.E. 
trend, fifteen miles long by five miles wide. Its platy or flaggy structure 
caused Sawkins to regard it as an altered sandstone. The associated rocks 
belong mostly to Sawkins’s Conglomerate Group, and are composed mainly of 
epiclastic igneous material, but they also contain some calcareous flags and a 
thick limestone (Good Hope or Halberstadt Limestone). An interesting volcanic 
episode has been discovered in the strata below the Good Hope limestone, where 
there are two or more flows of highly vesicular pillow-lava and some tuffs. The 
outcrops of the lavas have been found brought up by folding over an area nine 
miles in length. Also associated with the purple conglomerate group are 
gypseous beds. The gypsum was considered by Sawkins to be of secondary 
origin, and to have been formed by the action of sulphuric acid on the local 
limestones. But the discovery of pseudomorphs of rock-salt crystals among 
these deposits and the presence of salt springs indicate that the gypsum and 
rock-salt were precipitated by concentration of the water of a salt lake or 
marine lagoon. These minerals and their association with unfossiliferous purple 
and red rocks remind one of the Triassic rocks of England, and suggest that 
somewhat similar conditions once existed in Jamaica. The age of these deposits 
is probably early Eocene, though possibly Cretaceous. 
Hitherto no rocks earlier than Cretaceous have been recognised in Jamaica 
