THE STRATIFIED ROCKS OF ESSEX COUNTY. 39 
The microscopic structure as shown by five sections of this 
metaraorphic slate from East Haverhill is : angular and 
rounded grains of quartz in some of which there are nu- 
merous fluid inclusions, several quartz grains in the line of 
the schistosity of the rock-mass showing cracks from all 
the incipient stages to the broken and crushed masses, feld- 
spar grains much kaolin ized and showing the effect of 
crushing, some of the grains being broken into several 
pieces, scales of muscovite and biotite arranged in layers 
parallel to the schistosity of the rock-mass and inclusions 
of apatite, zircons, fibriolite and rutile abundant in the 
kaolinized feldspars. Titaniferous magnetite and leucox- 
ene are scattered through the sections and fine acute 
rhombs and long lath-shaped sections of titanite are seen 
in one of the thin sections. 
The microscopic structure of the metamorphic slate in the 
bed of the Merrimac river below the Lawrence dam is : 
clastic grains of quartz sand, some secondary quartz sur- 
rounded with earthy yellowish kaolin and chlorite masses, 
titaniferous magnetite and leucoxeneand a few grains of 
plagioclase with inclusions of apatite, zircons and fibrolite. 
The quartz grains show evidence of crushing, embryonic 
cracks are developed and some of the grains are broken 
and the pieces faulted two and in one instance three times. 
Nearly all of the bed rock of Methuen is composed of 
this metamorphic slate and a coarse mica schist of the same 
composition as that from Lawrence, Haverhill and Gage's 
Hill in Bradford. In Methuen this slate and schist is over 
one thousand feet in thickness ; the trend is north 40*^ east 
southwest, dip 45° west. Nearly every outcrop from West 
Andover across Lawrence, Methuen, Bradford, Haverhill, 
Merrimac, South Hampton, Hampton Falls and North 
Hampton to Rye in this strike is composed of these same 
metamorphic slates and schists. 
