THE AGATE BAY BEDS. 285 
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combed rock. In one place, about two miles below Lester River, one of 
the hard reddish-brown dense beds above referred to was furnished not only 
with an upper, but with a basal amygdaloid, in which the cavities were 
large, smooth-walled, and quite regularly oval, often empty, or lined with 
drusy quartz. 
A fine showing of one of these hard beds is to be met with on the 
coast near the center of Sec. 22, T. 53, R. 10 W., about ten miles above 
the mouth of Encampment River. Here is a bold cliff 25 feet high, of 
the hard, dense, light-brown rock, which below is without amygdules, but 
which as it is traced up the cliff becomes more and more amygdaloidal, 
finally becoming a highly vesicular amygdaloid, with large cavities elon- 
gated in a common direction, and carrying saponite, calcite and laumontite. 
Under the microscope the non-amygdaloidal portion of this rock is seen to 
be chiefly composed of tabular plagioclases (oligoclase) set in a brownish, 
iron-infiltrated matrix which will not affect the polarized light. Augite is 
present only in very rare minute rounded grains and in a few porphyritic 
crystals. Particles of magnetite and porphyritic oligoclases complete the 
list of ingredients. The rock is a diabase-porphyrite with the augite nearly 
or wholly wanting. 
Some of the less dense beds showed pseud-amygdaloidal phases, with 
pseud-amygdules chiefly of a dark-greenish chlorite, and at several points 
on the shore of Sec. 25, T. 51, R. 13 W., a crumbling pseud-amygdaloid 
was found with a light reddish color, mottled with dark-green chlorite 
pseud-amygdules, and presenting at first sight, especially on cross fract- 
ure, a strong resemblance to a reddish sandstone, with angular grains. 
This resemblance is heightened by the fact that the rock has a bedded 
appearance. A careful examination, however, of the weathered surface of 
the rock shows that it probably has a completely crystalline texture, and 
this is abundantly proved to be the case by the thin section, which shows 
that the rock is nothing but one of the usual pseud-amygdaloids, of inter- 
locking crystalline texture, and with no trace of fragmental origin. This 
rock would undoubtedly be taken for a sandstone by most observers at first 
sight. 
