Many of the pans of field-ice off Big Island had gravel strewn upon them. This was found to consist of gneiss with a certain proportion of darkly-colored schists. But on ice-pans further up the coast, or to the north-westward, I found fragments of shaly marl and of grey limestone with fossils, among which _Receplaculites Oweni_ was easily distinguished. Shells and bryozons, belonging to moderately deep-water species, were found on the same pans. The limestone fragments, just mentioned, would point to the occurrence of Silurian rocks on or near the great bays in the western part of the north shore of the Straits, where the land is said to be low. Dr. Franz Boas of Berlin has recorded the existence of these rocks in the interior of Baffin Land, only about two degrees of latitude north of this region. He says:[1] “Through the occurrence of the Silurian rocks on the Nettilling (Lake) the discovery of the same formation at the upper end of Frobisher Bay increases in value. We must now suppose that the Silurian limestones, which appear at Prince Rupert’s Inlet, extend from there to Frobisher Bay, and overlie the granites and gneisses of Baffin’s Bay and Davis’ Strait. We will not be far astray if we connect this extensive Silurian district with the limestones which occur to the south of Igluling, and which form the flat eastern half of Melville Peninsula. Southward from Nettilling, these rocks rise into low hill-ranges, which are indicated on the sketch by Padloaping.” [Footnote 1: Page 50 of Dr. A. Petermann’s Mitteilungen aus Justus Perthes Geographischer Anstalt, Nr. 80. Gotha, November, 1885.] [Sidenote: White Bear Sound.] In a letter to me, referring to the geology of Baffin Land, Dr. Boas says: “The most interesting geological problem of the country is a study of the line of division between the Silurian plains and the eastern highlands. I suppose that Silurian rocks will be found, either in the remotest corner of White Bear Sound, or close to it. Probably the strata will be found lying horizontally, and then soundings in the Lakes Amakdjuak and Nettilling, will be of great importance. It must be important for the problems of glaciation to survey the _inner_ rim of the enormous basin formed by the chain of mountains of Davis’ Strait, the plateau of Nugumit, Kinguait, Sikosuilat, Southampton Islands and Melville Peninsula.” [Sidenote: Ungava Bay.] In my report of last year, it was stated that fragments of grey, drab and yellowish-fossiliferous limestone, apparently Silurian, were common near Cape Chudleigh. If the supposition be correct that the glaciation of Ungava Bay was from the southward out into Hudson’s Strait, and thence round Cape Chudleigh into the bed of the ocean, these fragments would indicate that the limestones from which they are derived exist somewhere in the bay, either under the water or on Akpatok Island, which is described as low and level. [Sidenote: Stupart’s Bay.]