SOUTHERN PART OF THE PORCUPINES. 47 



sandstone outcrops where these occur, but the rock in place is rather too 

 soft to preserve such traces well had they existed upon it. The peculiar 

 greenstone of the Rocky mountains before referred to is not infrequent at 

 all levels, and as this particular rock occurs in place in the mountains (as 

 an interbedded layer) scarcely as far north as latitude 49° 30', it must 

 have traveled in a northeastward direction in order to reach this part of 

 the Porcupine hills. The matrix of the gravels, wherever seen, is a whitish 

 silty or sandy material, perhaps in part composed of disintegrated sand- 

 stones of local origin, but including grains of similar composition to the 

 pebbles themselves. 



The fiat outlines of the hills in all this southeastern part of the Porcu- 

 pines appears to be in the main plainly due to water-levelling, although 

 assisted by the practically horizontal attitude of the sandstone beds. 

 From the highest point here reached the terracing of the hills may be 

 finely seen for many miles to the northward, but still higher and partly 

 wooded ridges to the westward showed toward their summits an alto- 

 gether different and rougher character, although fundamentally composed 

 of the same Laramie rocks. The highest terrace seen on the hills, near 

 the headwaters of Beaver creek, was very well marked, and was estimated 

 by eye from a distance to reach about 4,900 feet above sealevel. 



In continuing the inquiry it became evident^ necessary to examine 

 the higher ridges above alluded to, and this was accomplished from the 

 upper valley of Beaver creek, whence an ascent was made to the highest 

 point in that vicinity, locally known as Five-mile butte. In this region 

 the'total amount of foreign drift is less considerable and distinct terraces 

 are seldom observable, facts doubtless due to the shelter afforded by adja- 

 cent highlands on all sides, but particularly to that of the wide belt of 

 hills and ridges to the eastward. Our camp on Beaver creek was at an 

 elevation of 4,222 feet, and in ascending from it to Five-mile butte, on the 

 east side of the valley, the following notes were made : 



4,950 feet, a few well rolled pieces of Laurentian, Winnipeg limestone and Rocky 



Mountain quartzites. 

 5,070 feet, a few small Laurentian pebbles. 

 5,144 feet, Laurentian boulders 2 feet 6 inches through, Rocky Mountain limestone, 



quartzite drift and probably a little Winnipeg limestone. 

 5,250 feet, a projecting point on the high ridge showing abundance of well rounded 



Laurentian and quartzite drift. 

 At 5,300 feet the ridge becomes flat-topped and probably marks a terrace-level. It 



is strewn with numerous well rolled pebbles of eastern and western origin, 



including Laurentian, Winnipeg limestone, and Rocky Mountain limestone 



and quartzite. Some of the Laurentian boulders are 2 feet in diameter. 

 Above this level nothing but debris of local sandstones was found, the highest point 



of Five-mile butte being reached at 5,365 feet. 



VII— Bull. Geol. Soc. Am., Vol. 7, 1895. 



