
          the valley formation consists near the Devils' gate of a 
grayish micaceous sandstone and fine grained conglomerate
with a fine grained white sandstone. Proceeding twenty or thirty
miles up the valley we find a white sandstone alternating
with white clay and white clayey sandstone. At our encampment
of August 5th-6th we found a fine white clayey
sandstone, a coarse sandstone or pudding stone and white
calcareous sandstone. A few miles to the west of that
position we reached a point where the sandstone reposed
immediately upon the granite, which thenceforward along our
line of route alternated with a compact clay slate.
We crossed the dividing ridge on the 8th of August &
found the soil of the plains at the foot of the mountains on
the western side to be sandy, being the decomposition of
the neighbouring granite mountains. From Laramie's fork
to this point the Artemesia was the characteristic plant,
occupying the place of the grasses, and filling the air with its
odour of camphor and spirits of turpentine. On the morning
of the 10th we entered the defile of the Wind river mountains.
I hope that what I have hastily said above will enable
you to write a short preface to the catalogue and I would
be exceedingly indebted to you if you could send it with
the 2d part of the catalogue in order that I may introduce
it into the report. The work is now in the hands of the printer
but I will delay its publication some days until I hear from you.
Should you find it proper to refer in your preface to heights
above the sea I will fill up any blanks you may leave.
In a few days I will reply to some other points in your
letter and in the mean time beg you to let me hear from
you as soon as will suit your convenience, as I am exceedingly
pressed & should be very sorry to publish the catalogue
        