456 = J. W. Powell—Geological Structure of the country 
ceived. The 2d satellite touched the limb at 8" 30™ 12°75, 
was wholly within the limb at 8" 38™ 00%-25, after which it 
could be seen for a very few minutes. 
1873, March 17. 10P. mM. The 3d satellite was seen as a 
dull irregular shading upon the disc of the planet. It became 
a well defined brownish-gray spot as it neared the center, seem- 
ing to be preceded by a minute grayish spot, possibly denoting 
an irregularity in the shape of the satellite. Diameter of 3d 
satellite = 1’"8 as measured while in transit. 
1878, March 28. The equatorial belt was marked by two 
large white spots, which seemed to narrow and elongate in an 
uatorial direction as the planet turned. The shadow of the 
1st satellite passed from the disc at 7* 22™ 44°. 
Art. L.—Some remarks on the Geological Structure of a district 
of country lying to thé north of the Grand Caiion of the Colo- 
rado ; J. W. PoWELt. 
THE Colorado River’ of the West is formed by the junction 
of the Grand and Green; from this point the course of the 
river is a little west of south until the mouth of the Little 
Colorado is reached, and from this last mentioned point, 11s 
general course is to the west to the mouth of the Rio Virgen, 
where it turns again to the south. ; 
The Grand Cafion extends from the mouth of the Little 
Colorado to the foot of the Grand Wash, a narrow, abrupt, 
I propose, in this article, to discuss briefly some of the seage 
1 to phical and geological features of a district ‘f 
country lying to the north of the Grand Cafion and south 0 
the sources of the Sevier, east of the Colorado River, and west 
of the Grand Wash and Pine Valley Mountains. : 
The principal tributaries of the Colorado from the region 
under discussion, commencing on the west, are the Rio Virgen, 
the Kanab, Tapete River and the Paria. All of these cess 
for the greater part of their courses, run in deep gorges, 20 
this is true also of their tributaries ; so that the region is trav- 
ersed by a labyrinth of profound cafions. 
From a line some distance south of the Grand Cafion, to ® 
line somewhat north of this region, all the geological forma 
tions have a general dip to the north. To the south, the pet 
formations have — eroded away, and in going from he 
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