216 MINERALOGY AND LITHOLOGY. 
Mt. Washington. The lamination is sometimes quite even; but, again, its 
plane is waved, twisted, bent, and knotted in various ways. This variety 
of mica schist is the ordinary one among the highly crystalline strata. 
At some points, as, for example, at Bedford, the mica is in little scales, 
and is mostly biotite. This brings the quartz into prominence by the 
contrast of color. Sometimes, as at Wakefield and Epping, the crystals 
of the ingredients are so small and so intermingled, that the rock becomes 
nearly massive, and resembles certain basic eruptive rocks in hand speci- 
mens. A glance with the microscope tells the true nature. This type 
is more characteristic of the valley formations, where all the rocks seem 
to have been recrystallized under gentler agencies than were those which 
have heaped up the most highly crystalline strata in the mountains. 
Some schists in this valley appear to be half fragmental in type, and 
consist of schistose masses of sand bound together by scales of mica, and 
resemble itacolumite in a degree. 
Andalusite Mica Schtst. In this rock crystals of andalusite are promi- 
nent and characteristic. Such schists abound in the mountainous re- 
gion. Rarely the andalusite is quite well crystallized. Often it exists in 
rounded nut-like forms in the rock, which are very hard, and become 
prominent on weathered surfaces on account of their greater ability to 
resist decay. Often it is in long rude imperfect crystals, which are 
heaped together in tangled web-works. These crystals often decay in a 
peculiar manner. Sometimes the centre rots away and a cylinder is pro- 
duced, and sometimes both centre and outside resist while the rest of 
the crystal gives way. At some points the macled structure is very 
prettily developed, but where this is the case the schist loses its marked 
micaceous character and becomes argillitic. The condition of internal 
alteration, which is shown by the microscopic structure of andalusite 
crystals, has been already pointed out on page 106. In a microscopic 
section of a schist from the Notch, it is seen that besides the large crys- 
tals there are very minute crystals of andalusite. 
Fibrolite Mica Schist. Mica schist full of fibrolite is abundant in the 
same regions as is andalusite schist. Fibrolite appears to be much more 
stable than is andalusite, and consequently its fibres appear very clear 
and fresh in thin sections. Fig. 3 on Pl. 8 represents a section of a fibro- 
lite schist from the Notch, as it appears between crossed Nicols. In the 
