DRIFT DIVISION. 313 
11. The scratches on rocks in place, the transportation of boulders and blocks, and the scratching of 
some of the latter, were all contemporaneous. 
12. Scratches, grooves, furrows, and smoothed surfaces are frequently found on the rocks in place, when 
uncovered of the soil that has protected them from disintegration, over most parts of the northern 
portion of the United States, in the regions in which boulders and erratic blocks are found. 
13. These scratched, grooved and smoothed surfaces are found on the high mountain tops (but more 
abundant in the valleys that traverse them), on the sides of hills and mountains, in valleys, and 
in broad level tracts of country (like Ohio and Western New-York). 
14. Directions of scratches. By considering the numerous observations that have been made on this 
subject, I find that they conform in their directions to those in which currents would flow, if the 
country were mostly covered by water. In some parts, they correspond in direction to the main 
water-sheds of the country. In others they do not; but in most instances where they do not con¬ 
form, the cause may generally be seen by studying the topographical features of the country, 
and taking into consideration some phenomena of currents that will be mentioned in their proper 
place in a subsequent part of this discussion. 
Pot-holes. 
These are found on elevated ground, and present all the appearances of those formed at 
waterfalls by the gyration of pebbles (harder than the rock) at the present time ; and in situa¬ 
tions where neither the highest floods, nor any causes acting as they do at the present time, 
could produce them. I have seen but two examples : One near the mouth of the Riviere aux 
Liards, elevated from fifty to one hundred feet above the level of the St. Peter’s river, in Iowa 
territory, and mentioned in the table of scratched and smoothed rocks ; the other at the Little 
falls of the Mohawk, and described by Prof. Vanuxem* and by others. 
Another example has been given by Prof. Emmons, in Antwerp, St. Lawrence county, 
N. Y. “ It is at least one hundred feet above the Oswegatchie, three-fourths of a mile dis¬ 
tant, with an intervening hill, higher by some fifty feet than this remarkable hole. This ledge 
of rocks skirts a valley on the west which is about one hundred rods wide, and its direction is 
about north and south. This hole is from twenty-four to thirty feet deep, and from twelve to 
fourteen feet in diameter, bearing the usual marks on the interior of water-worn surfaces. 
Upon the summit of the intervening high ground and the river, we find the polished rocks ; in 
one place a mass of the Potsdam sandstone still adhering to the primary, seven or eight feet in 
diameter, of an oval form, and about two feel thick, is all that remains of the stratum at this 
place, and grooved in the usual manner, with the scratches in a north and south direction.”! 
Another example of pot-holes is described in Grafton, New-Hampshire, on the crown of a 
high valley, on the divide between the waters of the Connecticut and Merrimack rivers, at an 
Natural History of New-York ; Geological Report of the Third District, 1842, p. 209. 
t Geological Report of New-York, 1840, pp. 351, 352. 
