Hoffman.] 210 [December 15, 



terminating upon the upper surface of a third layer of sand, upon 

 which rested a thin layer of fine charcoal, and larger fragments of 

 charred wood. The sand upon which the fire had been built was red- 

 dened by the heat to the depth of an inch and a quarter ; the overlying 

 layer retaining the natural tint, appearing as if the fire had been sud- 

 denly extinguished. The extent of the layer of ashes (or fine char- 

 coal) was about five feet in diameter, around which, at irregular 

 intervals, lay a number of dark blue silicious stones, also reddened 

 by oxidation on those sides facing the fire. Quite a number of frag- 

 ments of chipped quartzite lay scattered above and below this hearth, 

 in the same seam. About eighty yards up the river, another seam of 

 charred wood and ashes was exposed, also showing the red and burnt 

 condition of the gravel underlying it. It is a difficult matter to 

 advance any theory as to the age of these hearths. When the station 

 was established seven or eight years ago, the whole valley was cov- 

 ered with heavy timber. Stumps of cottonwood, sycamore and oak, 

 found standing nearly over the hearths, measured over four feet in 

 diameter, and trees of equal size are still flourishing both above and 

 below the station. 



The bluffs, which belong to the cretaceous formation, are filled with 

 fossil bivalves, and in several localities we find beds of dark blue 

 plastic clay, containing fossils, prominent amongst which are the Nau- 

 tilus Dekayi and Ammonites Placenta, which are found mixed with the 

 drift detritus from the plains ; these are found in the upper stratum 

 only, as the second stratum, at the bottom of which the hearths lay, 

 was probably deposited when the river's course lay near the opposite 

 banks, where the cretaceous rocks do not protrude; it is well known 

 that rivers continually tend to shift their courses. For a distance of 

 five miles on either side of the station the valley is comparatively 

 straight, but within it the river winds considerably. Lyell 1 says of 

 the Somme, when, in one of its curves, the current crosses " its gen- 

 eral line of descent, it eats out a curve on the opposite bank, or in the 

 side of the hills bounding the valley, from which curve it is turned 

 back again at an equal angle, so that it recrosses the line of descent, 

 and gradually hollows out another curve lower down in the opposite 

 bank," till the whole sides of the valley " present a succession of 

 salient and retiring angles." 



The river is also working a deeper bed which is apparent; but 

 what length of time was consumed in depositing these strata of sftnd 



iXyell's Principles, p. 206. 



