468 • Reports and Proceedings — 



Cumberland Coal-field a long-continued alternation of the sliale and 

 sandstone allowed the formation of sixty-seven Coal-beds, only two 

 of which in the " Joggins Section " are of workable size. 



Jt is noticeable that in the Pictou and Cumberland Coal-fields the 

 most productive horizon is at the base of the Coal-measures, and, 

 comparatively speaking, of limited thickness. Thus at Pictou, the 

 lower 1300 feet hold fifteen beds, yielding 119 feet of coal. At 

 Springhill, in the Cumberland district, the lower 1000 feet of the 

 Coal-measures hold twelve beds, containing 51 feet of coal. The 

 overlying measures are more arenaceous, and hold a much smaller 

 proportion of coal in both districts. In Cape Breton Coal-field there 

 are now exposed only 1300 feet of productive measures immediately 

 overlying the Millstone Grit, and holding the workable seams. 



The question naturally arises if it might not be considered that 

 at one time the Cape Breton Coal-field may not have had a total 

 thickness of strata equalling that recorded in Pictou and Cumberland, 

 and that possibly the upper section was similar in development. 



The coals from these districts present several points of diiference. 

 Thus the slightly higher ash contents of the Pictou and Cumberland 

 coals may be connected with the predominance of the including beds 

 of Shale as compared with the more arenaceous measures of Cape 

 Breton, and a low ash percentage in the coals. 



Other differences between the districts may be referred to conditions 

 of deposition, foldings, drainage, etc. 



As yet the study of the fossils of the three districts does not show 

 any points of difference calling for remark, but this subject has not 

 yet received a share of attention equal to that bestowed on the points 

 of economic interest. 



The above and other differences between the districts are perhaps 

 more justly considered due to local differences of the deposition 

 extending over large areas than as marking distinctions between 

 individual and isolated Coal-fields. 



3. — The Value of detailed Geological Maps in Eelation to 

 Water- Supply and other Practical Questions. 



By W. Whitaker, B.A., F.G.S., of the Geological Survey of England. 

 n^HOSE maps of the Geological Survey of England in which 

 J. various divisions of the Drift have been coloured tell us, as 

 a rule, a very different tale from the corresponding sheets in which 

 the Drift is ignored, and it is only these Drift maps that really give 

 Us a true idea of the nature of the surface. Indeed in many districts 

 a geological map that does not show the Drift is comparatively use- 

 less for most practical purposes, at all events in a populous country 

 like England. Moreover, it is not enough merely to mass Drift as 

 such, but its constituent members should be fairly distinguished, not 

 merely with regard to their classification or relative age, but also as 

 to their composition, whether of clay, loam, or gravel and sand. To 

 illustrate this there are exhibited copies of the two versions of many 

 of the Geological Survey Maps of the London Basin, with and with- 



