THE STRATIFIED ROCKS OF ESSEX COUNTY. 37 
quartz and feldspar grains, numerous fiakes of muscovite 
with detrital angular fragments and pebbles of the quartz, 
feldspars colored with ferreous oxide, some e})idote and 
chlorite and threads of calcite. 
Continuing on the strike of this shale, there are two out- 
crops in the northeastern pai't of Topstield, one in Line- 
brook, a parish of Ipswich on Bull Brook, one in Rowley 
near John Dodge's mill and another near tide water be- 
tween Ipswich Village and Rowley. The microscopic 
structure t)f the sections from specimens in the cabinet of 
the Peabody Academy of Science from these localities is 
nearly the same as that of the last two from Topstield. 
Other outcrops of these clastic shales are frequent in the 
northern part of the county. There is on the south l)ank 
of the Merrimac near the Artichoke river, a large area of 
this shale much crumpled and distorted with the strike 
north and south and dip vertical. Nenr the point where 
Indian river empties into the Merrimac the shales are 
continuous for three hundred yards, and from Bradford 
across North Andover and South Lawrence, in a south- 
west course, they can be traced in an almost unbroken line 
to West Andover. On this strike the shales are bedded 
between the granite gneisses on the south iuid the meta- 
morphic slates on the north. 
At North Sangus, near the corner of Main and Oak 
streets, is an outcrop of metamorphic slate interstratitied 
with a quartzite, and on Main street two hundred yards east 
of the school house the hornblendic eruptive granite cuts 
directly across this metamorphic slate and includes large 
fragments of it. The strike of these metamorphic slates 
and quartzites is noi-th 20° E. parallel to that of similar 
beds at Lynnfield Centre. The microscopic structure of this 
metamorphic slate is : clastic quartz grains with many fluid 
inclusions, well-rounded grains of plagioclase, orthoclase 
