Dr. Daicaon — Geology of Prince Edivard^s Inland. 203 



III. — Notes on the Geology of Prince Edwaud Island, in the 



Gulf of St. Lawbence. 



By J. "W. Dawson, LL.D., F.R.S., Principal of McGill's College, Montreal. 



THE writer had the opportunity last summer, with Dr. B. J. 

 Harrington as assistant, to re-examine the rock formations of 

 Prince Edward Island, of which a notice was given in the second 

 edition of his ''Acadian Geology." The report of our reconnaissance, 

 which has been published by the local government, with a map, 

 sections, and figures of fossils, may be referred to for details ; but I 

 propose in this paper to notice a few points of general scientific 

 interest not dwelt on in the report. 



Prince Edward Island is crescentic in form, about 100 miles in 

 length, and lies in the almost semi-circular bend formed by the 

 southern shore of the gulf of St. Lawrence. It is one of the most 

 populous and best cultivated portions of British America. Its sur- 

 face, though low, is undulating and agreeably diversified with farm 

 and forest, and beautiful arms of the sea. Its climate is compara- 

 tively mild and insular, and its soil of excellent quality ; while the 

 marly beds of decomposing oyster and mussel shells in its bays and 

 creeks afford an apparently inexhaustible means of restoring the 

 productiveness of the fields. 



The prevailing formation is the Trias, which here, as in Nova 

 Scotia and in Connecticut, is represented principally by bright red 

 sandstone, sometimes mottled with white, and associated with oc- 

 casional beds of grey and white sandstone. Subordinate to these 

 sandstones are beds of red and mottled clay, of reddish concretionary 

 and conglomerate limestone, sometimes dolomitic, and of reddish 

 conglomerate with quartz pebbles and arenaceous cement. These 

 beds undulate in low synclinals and anticlinals, having in general 

 a north-east and south-west direction, and rise in some places to an 

 elevation of 400 feet above the sea. They are probably about 500 

 feet in vertical thickness. The lower half of this thickness, which 

 contains the limestone beds and also certain hard beds of conglomerate 

 and concretionary calcareous sandstone, may be regarded as an 

 equivalent of the Bunter sandstone ; while the upper portion, con- 

 sisting principally of soft red sandstone, with some beds of fine- 

 grained conglomerate, may be regarded as corresponding to the 

 Keuper. 



In the little isolated spot named Hog or George Island, there 

 occurs a limited mass of doleritic trap. It includes both the compact 

 and vesicular variety, and the latter has its cavities filled with a 

 white mineral, which Dr. Harrington ascertained to be Saponite. 

 This trap, which was first noticed by Dr. Gesner in 1847, appears to 

 be contemporaneous with the red sandstone, and is similar to that 

 which occurs on a much larger scale in connexion with the Triassic 

 sandstones of Nova Scotia and Connecticut. 



The Triassic beds have afforded no distinct marine fossils, but in 

 the lower beds some vegetable remains occur. One of these is a 

 small cycadean stem presented to me by Mr. J. W. Taylor, P.G.S., 



