I. Bowman — Atlantic Preglacial Deposits. 315 



beneath them, these sands dip gently to the eastward. Their 

 maximum thickness is 25 feet, with, however, many variations 

 in thickness, as will be explained in a later paragraph. But 

 slightly cross-bedded at the base, these sands become more 

 and more irregular towards the top, where they display excel- 

 lent cross-bedded structure, the upper eight feet of the layer 

 being exclusively of this character. The sands vary in tex- 

 ture from line at the bottom to coarse at the top, and show in 

 the same direction a decreasing amount of the clayey constit- 

 uent possessed throughout. Just above the clays on which 

 they rest the sands carry sufficient clay to render them some- 

 what plastic when wet. At the top of the sands where cross- 

 bedding is most marked the sands are dry and partially 

 indurated, so that the eroded edges retreat with a nearly verti- 

 cal face. The indurating process has been carried so far in a 

 few places that the material might almost be called a sand- 

 stone. Scattered fragments of sponge spicules occur here as 

 in the clays previously described, and an equal amount of 

 glauconite. The sands are very silvery in general appearance, 

 owing to the great amount of muscovite present, some of the 

 flakes attaining a size of from 4 to 6 millimeters. There is 

 no break in the series thus far described, every change being 

 slow with conformable relations throughout. 



(3) Red sands. — At the top of the white sands an uncon- 

 formity occurs, the eroded edges of the white sands being 

 overlaid by a layer of coarse and dark red sands with a maxi- 

 mum thickness of 10 feet. These red sands bear large quanti- 

 ties of muscovite, a smaller quantity of biotite, and also 

 exhibit cross-bedding of a much greater degree of amplitude 

 than that shown in the white sands. Occurring only in 

 patches between the white and red sands and never present 

 where unconformable relations between these two members 

 are exhibited, is a thin layer (1 or 2 feet) of black, coarse sand 

 composed of large grains of smoky quartz and with an admix- 

 ture of biotite. It is cross-bedded after the manner of the 

 red sands which overlie it. 



(4) Dark green sands and clays. — If fig. 1 be consulted, it 

 will be seen that below the stairway near the middle of the 

 figure the section shows greenish black sands and clays at 

 the level of the white sands and below the level of the red 

 sands. The whole face was so masked by talus and land- 

 slide material near the top of the bluff that extensive exca- 

 vation was necessary to determine the relations of the various 

 beds. Both series of beds were evidently in place and the 

 problem resolved itself into finding the line of contact between 

 the two. This was accomplished with the results shown in 

 fig. 2, which is an enlarged portion of fig. 1 at E. 



