Geol. Census of pebbles of Superficial drift. W. Fork of Milk R.

Granite Gneiss &c prevalent colours pinkish & greyish 68
Whitish limestone (one or two like Rocky Mt. lime) 19
Quartz 10
Chert 7
Porphyrite, resembling that of Buttes 3
Soft Sandstone, claystone, &c (local) 15
Ironstone (local) 5
Ostrea shell (local) 1
Quartzite or Silicious pebble drift 138
The latter includes a few undoubted fragments of slaty rocks (greenish & blackish) & many samples apparently intermediate between this & Quartzite &c but not clearly separable into either group. Have therefore enumerated the whole collection under one name as having probably come from the Mountains. General colours of Quartzite drift here, yellowish, brownish, whitish. Not so much red as in last sample, but otherwise very similar.

Though the Quartzite Drift probably from the Mts. presents some peculiarities. Much greater preponderence of yellowish & brownish quartzites & hard sandstones than observed in parts I have seen. Also comparative absence of slatey rocks &c of red & green colours.
At bases of Mts greenish prevalent colour of pebbles & many greenish slate pebbles (associated with blackish &c) as far out as First Crossing of Milk R. (see samples there examined). May not these softer rocks have been ground out before getting so