(388) 



however, and although this map was prepared from the latest 

 available maps of the United States Geological and Coast 

 Surveys, it must be considered as merely indicating the direc- 

 tions in which the waves and winds have worked in the past 

 and how they may be expected to work in the future, so far 

 as adding to the land area or modifying its topography is 

 concerned. 



At the present time the sand spit stage is well represented 

 by Race Point and Long Point, while Race Run and the inner 

 portion of Provincetown Harbor represent areas that are rap- 

 idl)' becoming converted from tidal flats into marshes. The 

 former location of the head of Race Run is plainly indicated 

 by the depression which lies between the present outer line of 

 low dunes along the beach and the twenty-foot contour parallel 

 with them, which latter represents approximately the former 

 shore line, at a time when there was nothing but a spit or bar 

 where the present shore line is now. Further than this, if 

 the submarine conditions are studied it may be seen that sev- 

 eral bars are in process of formation north of and parallel 

 with the shore, which, reasoning from our premises, are 

 probably destined to coalesce, form a spit, and eventually to 

 become a new outer coast line, with a "run" on the inner 

 side. 



That the whole of the existing land, from the Highlands 

 of Truro northward has been built up in this way, by succes- 

 sive series of such phenomena, could hardly be questioned 

 even if no other evidence were available than that offered by 

 the surface features, but additional evidence is afforded by 

 an examination of the character and arrangement of the 

 material which forms the land. Every particle is water- 

 worn sand or gravel or cobble stones. The latter two con- 

 stituents evidently represent the coarser beach shingle and 

 they do not occur anywhere above the level of high tide. 

 They never enter into the composition of the hills, although 

 they are known to be beneath them in many localities. The 

 sand represents the finer material and only such particles as 

 are fine enough to be transported by the wind are ever found 



