ABSTRACTS OF TAPERS 



61 



In cut number 2 a lower magnification of 50 diameters was used. Here tlae 

 abrupt change from winter to summer is seen. Near the top of the picture is 

 a layer of finer material, denoting very quiet water conditions for a short 

 period, and this again is followed by coarser material. In the entire summer 

 component there are six or seven such changes. When this clay was deposited 

 the water must have been relatively deep and very quiet, for the grains do not 

 average more than 1/800 of a millimeter. 



Cut number 3 is a section taken from the highest and thinnest seasonal 

 layers at Woodsville. Here the water was shallower and the materials less 

 abundant than in the layers lower down. The current action was more pro- 

 nounced, as indicated by the sizes of the grains. At the top of the summer 

 component and beginning of the fall and winter component some coarse grains 



Figure 



-Section of Clay, Woodsville, Netc Hampshire 



may be seen. Above this zone, however, the grains are extremely fine through- 

 out. The magnification in this case is 35 diameters. This coarse material at 

 the end of summer and beginning of fall is also characteristic of similar layers 

 in the Squantum slate, which is a glacial slate. 



I have given wind action as a possible explanation of the coarse grains 

 mingled irregularly, or in a definite layer, through the fine material of au- 

 tumn or spring. The beginning of cyclonic control of the atmospheric circula- 

 tion in early fall, with high winds, might very well blow coarse grains into 

 the basin of deposition before the winter ice cover had formed to prevent the 

 access of such grains to the deposit. In the spring the melting of the ice 

 cover, with its included sand grains, would allow these grains to settle to the 

 bottom. Some parts of the ice cover would have more dirt than other parts, 

 and this would explain the less frequent occurrence of coarse material in the 

 early spring horizon of deposition. In the autumn horizons the finding of the 



