296 



SCIENCE 



[N. S. Vol. XXV. No. 634 



Cliffs fronted by talus heaps of huge 

 limestone blocks were formed in the lower 

 Devonie of Michigan. The cliffs consisted 

 of the Marine calcilutytes and their debris 

 was incorporated in the Dundee calcar- 

 enytes. The breceiated limestone of 

 Mackinac Island is a characteristic portion 

 of these early Devonie talus heaps. 



Professor Grabau's paper was discussed 

 by Professors Lane, Foerste, A. M. Miller 

 and Foerste. 



The Naples Fauna in Michiffan: A. W. 



Grabau, Columbia University. 



The occurrence of the strata at the top 

 of the Traverse group with the Goniatite 

 fauna of the Naples horizon was described. 



Professor Grabau's paper was discussed 

 by Professors Ami and Bell. 



Types of Cross-Bedding and Their Strati- 

 graphic Significance: A. "W. Grabau, 

 Columbia University. 

 Four types of cross-bedding, the suba- 

 queous, or delta, type, the torrential type 

 and the teolian type, were considered. The 

 occurrence of the last two as evidence of 

 continental origin of the formations in 

 which they are found was discussed. The 

 type of cross-bedding of the Pottsville con- 

 glomerate bears out the conclusions already 

 reached from its overlap relations, namely, 

 that this formation is of fluvial origin. 



Professor Grabau's paper was discussed 

 by Professors A. M. Miller, W. G. Smith, 

 Fairehild, Grabau, Lane, Ami, Fairehild, 

 Grabau, Lane, Hovey, Woodman and 

 Grabau. 



The Cumberland Coal Basin, Nova Scotia: 

 J. Edmund Woodman, Dalhousie Univ., 

 Halifax, N. S. 



The paper described the Carboniferous 

 and Permian rocks of this basin, especially 

 with reference to the source of material, 

 and the great overlap produced by the New 

 Glasgow conglomerate. From the struc- 



ture and lithology of the basin, the follow- 

 ing conclusions are reached: 



(1) That the sediments were laid upon 

 a differentially sinking floor, the shore line 

 a variable one against the Cobequid range 

 to the south, the detritus of the sediments 

 being directly derived from these moun- 

 tains; (2) conditions favorable to the 

 formation of coal existed over a large part 

 of the area bounded on the north by the 

 outcrop of the Joggins zone of seams, on 

 the east by the Springhill district, on the 

 south by the Cobequid mountains, and on 

 the west by a line down the middle of 

 Chiquecto bay; (3) these conditions be- 

 came adverse shoreward, because of the 

 violence of wave action, and seaward, 

 through deepening of the water; (4) 

 through the differential sinking of the bot- 

 tom and shore, beginning during the time 

 of the coal measures and continuing into 

 the Permian, slight in amount in the east 

 and increasing westward, an overlap of the 

 Permian upon the Cobequids has been 

 established, burying the coal horizons over 

 all the southern part of the basin except 

 the east end; (5) the horizons containing 

 the Joggins and Springhill seams extend 

 under the basin, blanketing at a consider- 

 able depth, and rising westward, outcrop- 

 ping under the center of Chiquecto bay on 

 the west; (6) this horizon swings eastward 

 at the north, appearing on the shore at 

 the Joggins, and eastward at the south, 

 plunging beneath the Permian overlap 

 before reaching the shore, hence covered 

 at all points on the south side of the basin ; 

 (7) it is probable that coal occupies this 

 horizon throughout this area, as indicated 

 by the pei-sistence of the Joggins zone of 

 seams, the abundance of the Springhill 

 coal, and the occurrence of a thick seam 

 at 2,250 feet in a borehole at FuUerton 

 laie, less than half-way from the shore of 

 Chiquecto bay to Springhill; (8) the sum- 

 mit of the Coal Measure should lie against 



