36 THE STRATIFIED ROCKS OF ESSEX COUNTY. 
otite, some muscovite and an abundance of magnetite in 
the planes of the schistosity of the shale, fine inclusions of 
micro-zircons are seen in the kaolinized feldspars. Some of 
the dark opaque patches resemble lignite and it is not im- 
possible that this shale is carboniferous, although it re- 
quires more field work and lithoh)gical study to prove it. 
In the line of the strike to the northeast, across the Ips- 
wich river in Topsfield, on the land of Mr. Peterson, two 
hundred yards northwest of the old Endicott copper mine, 
this shale, which is here a dull red color, protrudes in 
several pluces. It is interstratified with a ferruginous 
sandstone ; the strike remains constant, northeast to south- 
west with the dip 50° west. The microscopic structure of 
thin sections from the outcrop near the roadside is as fol- 
lows : section cut across the bedding, ground-mass of earthy 
kaolin much discolored with a ferruginous iron oxide, mag- 
netic titanic iron, some leucoxene, original quartz grains 
showing secondary enlargements, incipient cracks and bro- 
ken grains and also fluid inclusions, some feldspars much 
decomposed, muscovite scales, green chlorite, apatite, nu- 
merous microliths and zircons, a few grains of zoisite and 
epidote. A strongly developed shearing to the north ac- 
counts for the crushed and broken appearance of the quartz 
and feldspar grains. Section across the bedding from a 
specimen of the outcrop in the field on the opposite side 
of the road, near the dwelling house of Mr. Peterson : 
ground-mass composed of earthjdiaolin and fibrous chlorite, 
magnetite, titaniferous iron surrounded by leucoxene, 
micro-zircons, apatite, numerous microliths so small that 
they cannot be determined with the highest power of 
the miscroscope, quartz grains with numerous fluid inclu- 
sions, muscovite and a few grains of zoisite are arranged 
parallel to the bedding. Ferruginous sandstone from 
Peterson's land, Topsfield (Sec. 81) : ground-mass of 
