1875.] 407 [Dodge. 



In slate (e) of this vicinity, there are many obscure intimations of 

 living organisms sufficient to encourage careful and prolonged search. 



There is a small peculiarity, which, occurring in the slates of sev- 

 eral localities, may be valuable as indicating a connection between 

 them. I have seen it in the slate in place at Elm St., Somerville, and 

 Adams St., Quincy, and in slate pebbles in a comglomerate-erratic in 

 Randolph, and most abundantly of all in pebbles in a glaciated ledge 

 of pudding-stone in place north of Union Square in Brighton, where, 

 I believe, it was first noticed by Dr. Wyman of Cambridge. My at- 

 tention was called to it there by my friend, Mr. Morrill Wyman, Jr. 

 It consists in a somewhat indistinct marking of dots and lines on 

 the surfaces, which seems to be produced by the transverse and lon- 

 gitudinal sections of some small object imbedded in the slate. The 

 largest are about three-eighths of an inch long and of a diameter 

 about one-fifth or one-sixth of this length. They are cylindrical and 

 hollow as is shown by the annular transverse and oblique section; and 

 tapering, as appears when they lie flat on the surface, in which case 

 it often happens that they are polished down by glaciation so far as 

 to show a longitudinal depression midway of the width. Occasionally 

 a convex end appears, projecting too slightly to have been worn off*. 

 This condition is very deceptively imitated by a projecting grain of 

 sand; and indeed, fine as is the texture of the slate, the markings are 

 all so obscure that it is only after examining a large number with and 

 without a lens, that one feels assured that they may not all be referred 

 to crystallizations or other small accidental irregularities of the rock. 



B. Conglomerates. 



In this vicinity, as at Newbury and at Newport, the conglomerates 

 are largely developed. It is not easy to mark their exact extent in> 

 this vicinity. Boulders occur both to the north and west of any 

 places where I have seen the rock in place. Thus, I have found them 

 in Maiden and in Somerville, and it is said they have been thrown 

 up on Nahant east beaches. 1 Then, too, they are abundant about 

 Wellesley in Needham. As already intimated, there may very well be 

 detached localities among the crystallines not exposed to view but 

 from which these erratics were derived; or such deposits once existing 

 may have been entirely worn away by the same glacial action which 

 detached the boulders. 



i W. Prescott: — Essex Co. Soc. Nat. Hist., 1852, p. 79-91. 



