115 



Carbonate of lime .... 



45.67 



Carbonate of magnesia . 



8.97 



Pro to-carbon ate of iron 



21.76 



Proto-carbonate of manganese . . , 



16.10 



Silica and alumina .... 



3.34 



Loss 



4.16 



100 



It is interesting to observe that a substantial agreement exists 

 between this analysis, and that made by Miss E. H. Swallow, 1 

 of the siderite occurring in the gangue of the vein of argen- 

 tiferous galena at the Chipman Mine, about a mile north-west of 

 the limestone. 



The limestone in Lynnfield is far more serpentinic than that 

 in Newbury. The serpentine appears to be everywhere present 

 and abundant ; in fact, Prof. Hitchcock did not seem to regard 

 this rock as limestone at all, but described it under the head of 

 serpentine ; and a specimen analyzed by Dr. C. T. Jackson 

 contained no calcic carbonate. There is no doubt, however, 

 that the rock as a whole is a very serpentinic limestone. There 

 can be no question about the indigenous nature of this limestone, 

 for it is distinctly stratified ; and a glance at the map will show its 

 intimate relations with the regular stratified group on the west. 

 But few exposures of this serpentinic limestone have been ob- 

 served, and yet these are so disposed as to indicate that it covers 

 a considerable area ; and the distribution of the limestone 

 boulders in the drift to the southward tells the same story. I 

 have mapped it chiefly in accordance with the views of Prof. 

 Hitchcock and the observations of Prof. Hyatt. Toward the 

 east the limestone is met by unstratified diorites, and in general 

 the petrologic relations appear to be the same here as in 

 Newbury. 



Next in order is the well-known dolomite in Stoneham. 

 This is not serpentinic, but holds the allied mineral, bowenite ; 

 and, although of a beautiful white color, it contains less than 



1 Proc. Bost. Soc. Nat. Hist., xvn., 464. 



