1890.] PUBLIC DOCUMENT — No. 4. 299 



ice, the coarser particles quickly fell upon the surface of the 

 land or upon the sea floor; while the finer mud, supported 

 for a long time in the water of the rivers or tidal currents, 

 was carried far from the margin of the ice field. Generally 

 speaking, the clay escaped from the field of the ice action, 

 and was borne away to the ocean floor or to the level plains, 

 such as have accumulated about the mouth of the Mississippi. 

 We find the only considerable remnant of the material borne 

 out by the subglacial rivers in the sand plains, which are 

 extensive developed deposits along the coast line of New 

 England south of Maine, or across the face of the continent 

 in front of the open ice margin, from the Atlantic Ocean to 

 the far West. 



These glacial sands, composed of the materials poured 

 forth by the old rivers from beneath the ice, constitute a 

 marked feature in the soils of Massachusetts. Besinnino: in 

 the western margin of the State, we find traces of these 

 deposits, as is shown in the general map, along the bottoms 

 of the greater valleys, usually forming a narrow strip, extend- 

 ing from near the head waters of these streams to their con- 

 fluence with the larger rivers. In these larger rivers the 

 deposits are to a great extent continued ; but they are in a 

 considerable measure hidden by recent alluvial accumulations 

 which have occurred in such places. In the Berkshire dis- 

 trict, as we may term the hilly country west of the Connect- 

 icut, the proportion of the area occupied by these washed 

 sands and gravels is small. It does not amount to more than 

 one-tenth of the Avhole field, the remainder of the surface 

 being covered by till materials, as Ave may term the unwashed 

 waste of the ice time. East of the Connecticut the proportion 

 of these sands and gravels greatly increases, until, in the 

 section east of the meridian of Worcester, about three-fourths 

 of the area is covered by these washed materials. 



As will be readily noted by the observer, the greater 

 part of the detrital matter composing these stratified gravels 

 and sands is of a silicious nature. Generally, however, 

 there is a certain admixture of pebbles of compound rocks, 

 fragments containing a certain amount of lime, potash, soda 

 and phosphatic material, which supply them in a small meas- 

 ure the materials necessary for the sustenance of plants. It 



