300 BOARD OF AGRICULTURE. [Jan. 



is a well-known fact that pure quartz yields but little of the 

 material necessary for plant growth. In our soils quartz has 

 something of the same place in the general functions of the 

 material which nitrogen has in the air. It is practically an 

 inert substance, entering into but few combinations, but 

 serving to dilute the other materials which compose the soil 

 material. Plants will not develop in pure sand, any more 

 than animals will breathe in pure nitrogen. On the other 

 hand, a soil entirely destitute of silicious matter Avould be 

 unfruitful, because of the excessive compactness which would 

 thus characterize it. 



There is a third condition of the soil in a glaciated field, 

 which is due also to a peculiarity in the physical conditions 

 of the last ice time. During the glacial period, the front or 

 margin of the ice occupied a number of different positions. 

 At one time this ice front was maintained for a consideral)le 

 period, probably for some thousands of years, along the line 

 beyond the margin of the main-land. It stretched from 

 southern New Jersey across where now lies Long Island, 

 N. y., thence by the islands of Martha's Vineyard and the 

 main-land of Cape Cod, extending farther to the northward 

 across the gulf of Maine. At later stao-es in the decline of 

 the great glacier, this front occupied for a less considerable 

 period various positions farther in the interior of the country. 

 Alono; the successive mars-ins of the ice there were accumu- 

 lated heaps of detritus known as frontal moraines. These 

 frontal moraines are an extremely conspicuous feature across 

 the greater part of the continent. They are characteristically 

 shown on Long Island, N. Y., on Martha's Vineyard, Nan- 

 tucket, and at other points in south-eastern Massachusetts. 

 Similar deposits, indicating shorter periods of action, are 

 traceable throughout Massachusetts from the Connecticut 

 River to the sea. 



These shoved moraines represent a very complicate/, 

 series of actions. In part they are due to the fact that 

 the ice, moving constantly forward, was melted, and passed 

 into the state of water along the line of the glacial margin, 

 and so dropped the detritus which had become mixed with 

 its mass in the long journey over the bed rock. It is 

 evident also that the front of the ice was not permanent, and 



