GEOLOGICAL AND MINERALOGICAL NOTES. 71 



lines, determined by the absence of drift and by water 

 worn ledges, at elevations from fifty to one bundred and 

 fifty feet above the sea. At elevations from twenty-five 

 to one hundred feet above the present sea level, noticeably 

 at Turkey hill and Town hill in Ipswich, Grasshopper 

 piain and at Pipe-stave hill in West Newbury, and also in 

 many places on the Merrimac River at Haverhill and Law- 

 rence, there are nunierous areas of sand similar to the 

 beaches of our seacoast at the present time. But as no 

 remains of a marine fauna have as yet been obtained from 

 these so-called inland beaches or from the talus of the 

 cliffs, it is highly improbable that they all belong to the 

 Champlain epoch. It is much more probable, however, 

 that they should chiefly be referred to the Terrace epoch. 

 Prof. J. D. Dana says (Manual of Geology, p. 557) : 

 ff The height of the upper terraces of river Valleys and 

 lakes was largely an effect of the height of the flood and 

 not necessarily of a subsequent change of level of the con- 

 tinent." 



In relation to the height of the sea level since the Gla- 

 cial period, Professor Shaler says in the report previously 

 mentioned (p. 571) : " The imperf ect evidence which I 

 have succeeded in obtaining on the Cape Ann district serv- 

 ing to show the action of the sea above its present level 

 is limited to 150 feet above the present tide mark." These 

 evidences certainly appear to be capable of two interpre- 

 tations : — first, action of the waves when the sea was at a 

 greater height ; and, second, decay in situ of weaker rock 

 surfaces resulting from atmospheric causes. Dykes beyond 

 the reach of the action of the sea at its present level, which 

 have been disintegrated, are taken as evidence that the sea 

 must at some time have been at that level. But there are 

 numerous dykes on Salem Neck at about the same level as 

 those referred to by Professor Shaler, which have decay ed 



