272 B. K. Emerson — " Bernard ston Series'''' of 



reinforces the stratigraphical for the continuity of the lime- 

 stone and the quartzite. At its northern end, overhanging 

 the brook in the most northerly digging, the magnetite la} T er 

 is a black, magnetite-pyrite-chlorite rock. Fig. 4, and e, tig 2. 

 This rock which caps the limestone contains amphibole, biotite, 

 chlorite and little pyrite, magnetite and hematite, and an 

 amorphous mineral resembling serpentine. The biotite is very 

 dark colored in basal sections and in places changing into 

 chlorite and passing at the edges into the serpentine-like min- 

 eral. In the larger part of the section it has a fibrous 

 structure the fibers grouped into large elongate patches, at times 

 radiate and the whole resembling a fine hornblende schist. It 

 is of oil-green color, shows only in patches a trace of dichroism, 

 and with polarized light there is a faint predominance of 

 extinction at about 3° from the long axis of the fibrous groups, 

 which proceeds from the whole group ; and this is overlaid as it 

 were by the aggregate polarization of the serpentine-like mineral 

 in fine scales and needles. An analysis made for me by Mr. G. 

 H. Corey, of the class of '88 in Amherst College, gave : 



Si0 2 42-56, Fe 2 3 44-25, CaO 13-11 = 99'92. 



The absence of magnesia from this analysis is puzzling, as the 

 product of decomposition of the hornblende resembles ser- 

 jDentine strongly. It is possible that a highly ferruginous 

 amphibole has developed in the magnetite-calcite bed and this 

 has changed into a ferruginous mineral allied to chloropal. 



h. The eastern bed of Quartzite. — Under the birches, as repre- 

 sented in the section, fig. 4, one meter of a thin, evenly lamin- 

 ated, light gray quartz-schist caps the limestone, and is very 

 rusty especially at the base, and porous from the ainount of 

 pyrite and calcite that has been removed. Two-thirds the way 

 up a layer of about 10 cm thickness is crowded with flattened 

 and distorted casts of Brachiopoda and of annulate Crinoid 

 stems ; a large Spirifer, with septa like S. disjuncta, is 

 very abundant. Traces also of Rkynchonella and Orthis are 

 common, of JVucula and Blatyostoma rare, and the ringed 

 Crinoid stems again very common. The material I have been 

 able to obtain has been submitted to Mr. J. P. Whitfield and 

 discussed by him in this Journal.* The fossiliferous bed is of 

 very limited lateral extent, and I could trace it only about 

 three meters. 



The next outcrops, 15 m. east, and about 2 m. above the bed 

 just described, is a hard gray quartzose conglomerate, with 

 white flattened quartz pebbles, 10-25 mm across. Under the 

 microscope, the rock is seen to be made up of angular grains, 

 with large cavities filled with water, containing spherical 



* Vol. xxv, page 368, 1883. 



