H4 THE CANADIAN NATURALIST. [Vol. viii. 



this change was a gradual one, or was brought about by sudden 

 and repeated elevations of the land. The mode by which the 

 shoaling of the Post-Pliocene sea was effected is explained, 

 however, by the existence of terraces at several levels on the 

 land near the coast. The change of level was, it would seem, 

 accompanied by rapid elevations, separated by intervals of rest, 

 and the amount of these periodic changes of level can (with cer- 

 tain allowances for the peculiar tidal phenomena of the Bay of 

 Fundy) be estimated with an approach to accuracy. Any 

 indentation of the shore Hue along the coast where sediment 

 could accumulate subject to the wash of the waves, would have 

 sand flats extending to the lowest limit of tide, and in the B;iy 

 of Fundy, where the rise and f Jl of the tides is very great, such 

 flats would have a slope seaward of twenty or thirty feet : if 

 such a plain were lifted above the sea level and terraced by the 

 action of the waves, the resulting terrace would vary between 

 the limits indicated. This is found to be the case near St. 

 John, where the first terrace rises to the height of fifteen feet 

 above the sea. The next, which is much more conspicuous, varies 

 from forty to sixty feet ; and can be seen to be composed of the 

 three subdivisions of the modified drift; viz. Syrtensian beds, Leda 

 ; clay and Saxicava sand. A third terrace begins at the height of 

 about 100 feet and extends to 120 feet. The surface layers on 

 this terrace are coarser than those of the last and consist of stra- 

 tified gravel and sand. Another terrace of similar material was 

 observed at a height of 150 feet, and a fifth at 300 feet. Terra- 

 ces at this height are very gravelly, quite irregular, and cannot 

 always be distinguished from Syrtensian ridges. As those 

 ancient sea-borders are a memento of the rise of the land in 

 Post-Pliocene times, so the composition of the Leda clay in the 

 Southern Highlands of New Brunswick, furnishes a criterion 

 whereby one can judge of the depth of the sea during the whole 

 period occupied in its deposition. In these hills many of the 

 valleys are cut down nearly or quite to the sea level ; and while 

 they are partly filled with modified drift, the neighboring hills 

 are covered to a greater or less degree with Boulder-clay. Leda 

 clay forms a notable part of the modified drift in these valleys, 

 and rises up on their slopes to a height of 200 feet or more. 

 Very instructive sections of these deposits on the east-side of the 

 Nerepis and Douglas valleys in Queen's County were made in 

 grading the track of the E. and N. A. Railway : here, where 



