20 The American Geologist. January, 1901. 
tween the two minerals are very irregular. A few grains of 
chromic ( ?) iron form the only other constituent of the 
rock. 
The talc schists of slate are soft, greenish gray in color, 
and have the distinctive tlose or greasy feel. They are 
often finely laminated with a distinct cleaverage. In ordinary 
light the thin section appears colorless except for the pres- 
ence of small grans of iron or leucoxene, which are some- 
what evenly distributed throughout the field. Between 
crossed nicols the colorless mineral polarizes faintly in tints 
of gray. No crystal outlines are surely distinguishable in it. 
An earlier origin is assumed for the western than for the 
much larger eastern division of Orford mountain from a 
consideration of the following facts, most of which have been 
already stated. 
The serpentine and other metamorphic rocks are in a more 
advanced stage of alteration than the diabase, and are intri- 
cately associated with sedimentary rocks of Cambrian age 
and may be even older than these. The diabase and gabbro- 
dioryte mass, which, as has been said, forms the higher and 
greater portion of the mountain, contains little, if any, ser- 
pentine and clearly cuts strata recently determined on fossil 
evidence* to be of Cambro-Silurian age. Also, the serpen- 
tines, which with their associates occur very frequently along 
the southeastern side of the Sutton mountain anticlinal simi- 
larly associated with clastic rocks, without the presence of 
diabase at all, are here in a few instances cut by dykes, while 
no dykes have been found in the diabase. These dykes are 
too far altered to make it possible to determin their precise 
original characters. In the case of three near Orford pond 
the minerals augite, or secondary hornblende, are prominent 
constituents along with larger amounts of epidote, commonly 
in the form of zoisite, and in one case with a little quartz. 
They are not very different from the extremely fine, "apha- 
nitic," form of the diabase as seen near its contact with the 
slates about Miletta and hence very probably belong to that 
mass. 
•Dr. R. W. Ells, An. Rep. Ge&l. Survey of Canada, Part J., p. 38; Dr. H. 
M. Ami, "Preliminary Lists of Organic Remains," Appendix to the above, Part 
J., p. 133. Dr. Ells also points out that Serpentine rarely if ever occurs in 
masses intrusive through strata of Cambro-Silurian age, op. cit. p. 80. 
