524 MR. E. GILPIN ON THE GEOLOGY OE 



to the north and south. This formation generally presents the 

 aspect of a friable, reddish conglomerate, the pebbles varying in size 

 up to a diameter of three feet. The masses are frequently of little 

 coherence ; in some cases the matrix is calcspar, haematite, or quartz. 

 The conglomerates, the distinguishing feature of the formation, 

 alternate with beds and masses of red and grey, coarse- and fine- 

 grained, friable sandstones, and with beds of red and green marl 

 and an occasional bed of limestone. Usually the upper beds are 

 finer than those at the base, but many sections are largely made up 

 of conglomerates. 



Passing to the westward we meet the Carboniferous of St. Peter's 

 Bay and the Eiver Inhabitants. The marine limestone and some 

 representatives of the division just alluded to border St. Peter's Bay 

 and inlet and the northern shore of Isle Madame, and, passing under 

 the higher divisions, skirt the Sporting Mountains, and passing 

 round the head of West Bay, fill the valley of the Hiver Inhabitants, 

 and are exposed on the shore of the Strait of Canso at Plaster Cove. 

 In this group are included measures which resemble more closely 

 the typical Lower Coal-formation of Sir J. W. Dawson's 'Acadian 

 Geology ' than any met elsewhere in the island, and the tint on 

 the map really includes both the marine limestone and the lowest 

 division. These measures pass into the Eiver Denny's basin and 

 extend to the Grand Narrows. 



The officers of the Canadian Geological Survey have grouped the 

 Carboniferous measures overlying these subdivisions under the term 

 " Middle " Carboniferous, including the Millstone Grit, Productive 

 Measures, and beds referred with doubt to the Upper Coal-forma- 

 tion, as the dividing lines are obscure and the structure not yet 

 fully worked out. On the map the Middle Coal-formation districts, 

 as indicated by coal-crops, are marked by their appropriate tint, 

 and the remainder of the debatable ground is referred to the MiUstone 

 Grit. Mr. Fletcher gives the total thickness of the Carboniferous 

 strata at 21,960 feet, which probably embraces all the subdivisions 

 already described in the Sydney district ; and, possibly, the 1350 feet 

 of measures referred to by him as overlying the Little-Eiver coal- 

 series (8926 feet thick) may represent part of the Upper Coal-for- 

 mation, subdivision No. 1 of Sir J. W. Dawson. The measures do 

 not present many points of interest calling for special mention. It 

 may be rem.arked that the coal-beds and their extent are imper- 

 fectly known, and that they are not considered so valuable as those 

 met elsewhere in the island. Some of the sandstones and shales 

 of the Eiver Inhabitants are little more than compact sand and 

 mud, while at other points the rocks have the normal hardness of 

 the Carboniferous strata. * 



In describing the Carboniferous strata lying north of a line drawn 



from Baddeck through Whyhogomah Bay to Low Point, Mr. Eletcher 



has adopted the following classification : — 



p , .. /Middle: Millstone Grit and Middle Coal-formation, 



UarDomterous | j^^^^^ . Conglomerate and Marine Limestone ; 



but I have followed the regular classification on the map. 



