No. 8.] MATTHEW GEOLOGY OF NEW BRUNSWICK. 453 



into the sea at the submerged foot of the glacier, beneath which 

 it was formed. 



The history of the surface deposits in Acadia, so far as I 

 have traced it, might, upon these grounds, be briefly stated as 

 follows : — 



1. The StricE mark the formation of a glacial zone across the 

 continent, fticing an open sea to the south. 



2. In connection with the production of striae there followed 

 the accumulation of ice on the southern side of this zone, causing 

 a depression of the earth's crust, and producing the slope required 

 to give motion to the glacier covering the Acadian plain,* causing 

 also the suhmarine glacier-foot necessary to account for the 

 nature of the Boulder Clay. 



3. Recession of the glaciers to the North, consequent upon 

 the continuous sinkinsr of the land at their southern border. 

 This change would result in the widening of the submerged 

 tract, nnd the admission upon it of the arctic current from the 

 north-east; and would give rise to the formation of the Syrtensian 

 beds out of the Boulder clay, the finer material of which, in 

 tracts exposed to the wear of the current, would be carried off 

 to greater depths and more sheltered areas in the ocean. 



There is one subject which should be touched upon before 

 bringing these remarks to a close, namely, the time-value of the 

 Syrtensian beds: how will this epoch compare, for duration, 

 with that of the Boulder clay ? The gravel and sandy strata 

 of the former group do not present such a thick and uniform 

 coating of detrital matter as the latter, for, although they some- 

 times rise into ridges of 150 feet high, this thickness is excep- 

 tional, and there are large areas where the deposit does not 

 measure more than a score of feet in depth, and many spots 

 which are entirely bare. 



But, although the Boulder clay is, on the average, much 

 thicker, there are some considerations which depreciate its value 

 as a time-indicator. Previous to its formation, the eastern part 

 of the continent appears to have been for long ages above the 

 ocean, and the solid rocks, under the influence of a warm and 

 probably humid climate, had been decomposed to great dejjths. 

 In parts of A^irginia and North Carolina which have not been 

 beneath the glacier, the gneissic ledges are now softened to a 



* See p. 7 of former article on Surface Geolog)' of New Brunswick 



