AN ANCIENT DUNE. 51 



let for ordinary drainage — was deepened until the clay underlying 

 the coarse glacial gravel was exposed. The ordinary rains of a 

 season falling on ploughed ground may not have a marked effect, 

 but the rains of centuries tell another story. 



A section of this dune, cut to a depth of about six feet, shows 

 the present surface soil of about eight inches and of a brownish 

 color inclining to yellow, and beneath, a thick deposit of yellow sand, 

 or brownish-yellow, which is very compact, of uniform size of 

 grains and without any trace of stratification. This, more than 

 aught else, suggests that it is a wind-blown deposit from some 

 near-by point and subsequently compacted by pressure of an over- 

 lying stratum and the slow infiltration of moisture. 



This deposit, during severe winters, is frozen, nearly if not quite, 

 its whole depth, but this and the subsequent disappearance of frost 

 does not affect its structure, except to gradually render it more 

 compact. 



This yellow sand is but a continuation of the present surface 

 soil, the difference in color being due to stain from the yearly coat- 

 ing of broadcasted barnyard manure and the decomposition of 

 vegetation. 



The deposit merges into a greenish sand, of somewhat coarser 

 grain and looser texture, which in turn rests upon coarse gravel and 

 this on the clay — possibly pre-glacial. 



This uniform structure of the deposits is not confined to the 

 entire area or the conical hill to which reference has been made. 

 Near the center of it we meet with irregular bands of red clay of 

 varying thickness and of more varying length. This clay is in no 

 sense a continuous deposit of this material as when the Raritan or 

 Pensauken clays were laid down, nor are they derived directly from 

 them. I should say they are due to gradual infiltration when the 

 texture was looser than at present and so a deposit of argillaceous 

 character from overlying sand and the actual surface carried to 

 where the more compact sand checked the water — summer rains and 

 melting snows — and the particles held in suspension were arrested. 

 This once started, the water would be held here, later, until all for- 

 eign matter was deposited. Even now, there is very little sand to be 

 found here, that is even approximately clean, and the sand of this 



