GEOLOGICAL REMARKS. 
185 
In turning an angle of the river, however, a broad reach 
stretched away before us. An alluvial flat extended to our left, 
and a high line of cliffs, that differed in no visible respect from 
those we had already passed, rose over the opposite side of 
the river. The cliffs faced the W. N.W., and as the sun 
declined, his beams struck full upon them. As we shot 
past, we were quite dazzled with the burst of light that 
flashed upon ns, and which gave to the whole face of the 
cliff the appearance of a splendid mirror. The effect was 
of course momentary ; for as soon as we had passed the 
angle of refraction, there was nothing unusual in its appear- 
ance. On a nearer approach, however, it appeared again 
as if studded with stars. We had already determined on 
examining it more closely, and this second peculiarity still 
further excited our curiosity. On landing, we found the 
whole cliff to be a mass of selenite, in which the various 
shells already noticed were plentifully imbedded, as in ice. 
The features of the cliff differed from any we had previously 
remarked. Large masses, or blocks of square or oblong 
shape, had fallen to its base, and its surface was hard, 
whereas the face of the majority of the other cliffs was soft 
from the effect of the atmosphere ; and the rock was entirely 
free from every other substance, excepting the shells of 
which it was composed. We of course collected some 
good specimens, although they added very considerably to 
the weight of our cargo. 
The morning of the 1 8th was calm and cloudless. The 
wind, of which there was but little, came from the north, 
