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leave only casual places at which they can be entered by 
horses. The road across the country, which would otherwise 
be very good, is rendered impracticable for wagons by these 
streams. At such places, the gun-carriage was unlimbered, 
and separately descended by hand. Continuing a few miles up 
the left bank of the river, we encamped early in an open 
bottom among the pines, a short distance below a lodge of 
Indians. Here, along the river bluffs present escarpments 
seven or eight hundred feet in height, containing strata of a 
very fine porcelain clay, overlaid, at the height of about five 
hundred feet, by a massive stratum of compact basalt one 
hundred feet in thickness, which again is succeeded above by 
other strata of volcanic rocks. The clay strata are variously 
colored, some of them very nearly as white as chalk, and very 
fine grained. Specimens brought from these have been sub- 
jected to microscopical examination by Professor Bailey, of 
West Point, and are considered by him to constitute one of 
the most remarkable deposits of fluviatile infusoria on record. 
While they abound in genera and species which are common 
in fresh water, but which rarely thrive where the water is 
brackish, not one decidedly marine form is to be found 
among them; and their fresh-water origin is therefore 
beyond a doubt. It is equally certain that they lived and 
died at the situation where they were found, as they could 
scarcely have been transported by running waters without 
an admixture of sandy particles; from which, however, they 
are remarkably free. Fossil infusoria of a fresh-water origin 
had been previously detached by Mr. Bailey in specimens 
brought by Mr. James D. Dana from the tertiary formation 
of Oregon. Most of the species in those specimens differed 
so much from those ‘now living and known, that he was led 
to infer that they might belong to extinct species, and con- * 
sidered them also as affording proof of an alternation in the 
formation from which they were obtained, of fresh and salt 
water deposits, which, common enough in Europe, had not 
hitherto been noticed in the United States. Coming eyi- 
dently from a locality entirely different, our specimens show 
very few species in common with those brought by Mr. 
