Observations on the Stratification of Slate. 223 
river on the road by which Mr. Hunt had passed in quest 
of Indians, and have not since been heard of. Mr. C. had 
followed Mr. H’s track in the snow for seven days: but 
coming to a low prairie, he lost every appearance of the 
trace, and was compelled to pass the remaining part of win- 
ter in the mountains, subsisting sometimes on beaver and 
horse meat, and their skins, and at others on their success 
in finding roots. Finally, on the Jast of March, the other 
only Canadian, being unable to proceed, was left with a 
lodge of Shoshonies; and Mr. C. with John Day, finding 
the snow sufficiently diminished, undertook from Indian 
information to cross the last ridge, which they happily ef- 
fected, and reached the banks of the Columbia by the mid- 
dle of April, where, in the beginning of May, they fell in 
with Messrs. Steuart, having been a few days before strip- 
ped of every thing they possessed by a band of villains near 
the falls. On the 10th of May they arrived safe at Astoria, 
the principal establishment of the Pacific Fur Company, 
within 14 miles of Cape Disappointment. 
XL. Observations on the Stratification of Slate. By Mr. 
WILLIAM CREIGHTON. 
To Mr, Tilloch. 
rer pes, bs your Jast number, page 116, Mr. Farey accuses 
Mr. Bakewell of inaccuracy in describing the stratification 
of slate, the peculiarities of which can scarcely have escaped 
observation ; but I am induced to offer a few remarks there- 
_upon, as the work of Mr. Jameson the geognost is imper- 
fect, and Mr. Bakewell’s Introduction to Geology not sa- 
tisfactory on this subject, with which Mr. Farey seems 
unacquainted. 
The lamine of argillaceous schistus are not only found 
perpendicular to the stratification, but form various angles 
with it, which arises from the strata being thrown into 
waves having different widths and steepness of sides, with 
-a considerable proportionate length: the schistus of these 
strata has its laminz perpendicular or nearly so to the hori- 
zon, and in the same direction as the length of the waves : 
it has therefore a diversity of angles to the stratification : 
and as the perpendicular depths continue the same, the 
transverse thickness 13 greatest at the top and hollow of the 
waves, gradnally becoming more or less thin on the sides, 
according to their declivity: when strata of grau-wacke al- 
ternate, the thickness of them is nearly uniform, in which 
‘ respect 
