478 



SCIENCE. 



[Vol. I., No. 17. 



was observed to be associated with stratiiied 

 sand-beds. 



Eesting upon the shingle deposit in some 

 localities, but in other places directly on the 

 cretaceous and Laramie, is the bowlder-claj', 

 a mass of sandy claj-, often very hard, and not 

 infrequently showing a pretty well marked rela- 

 tion in colors and material to the underlying soft 

 rocks, from which it has evidently been largely 

 formed, but packed irregularlj' with bowlders 

 and fragments of Laurentian and Huronian ori- 

 gin, often distinctly glaciated, and with quartz- 

 ite pebbles resembling those aibove described. 

 While generalljr rather massive in character, 

 the bowlder-claj'' is frequently more or less evi- 

 dently divided by stratification-planes, and is 

 quite distinct in appearance from the morainic 

 accumulations which occur in the foot-hill belt. 



The upper part of the bowlder-clay is usually 

 much more distinctly stratified than the lower, 

 and often more or less markedly lighter in 

 color, though still holding numerous stones 

 and bowlders of mingled Laurentian and Rocky 

 Mountain origin. In the region through which 

 the lower part of the Belly River cuts, a series 

 of well- stratified sands and sandj' clays are in- 

 tercalated between these two divisions of the 

 bowlder-clajr ; and in several sections these were 

 observed to include an irregular laj-er of impure 

 lignite or indurated peat a few inches in thick- 

 ness, evidently the accumulation in a swamp or 

 shallow lake which must have covered many 

 miles of surface. A thin nodular deposit of 

 ironstone was also found in association with 

 the lignite at one place. This is the first evi- 

 dence of an interglacial period, or interruption 

 of the severity of the glacial conditions, which 

 I have met with in the area of the great plains ; 

 but the facts are here perfectly clear and con- 

 clusive. 



The surface of the plains generally is often 

 strewn more or less thickly with erratics, which, 

 except in the immediate vicinitj- of the moun- 

 tains, are usually derived from the Laurentian 

 axis ; and, as they are frequently larger than any 

 of those characterizing the bowlder-clay of the 

 neighborhood, there is reason to believe that 

 the}' belong to a subsequent period of disper- 

 sion. Several very large bowlders of Huronian 

 quartzite occur near the Waterton River, not 

 far from the western limit of the Laurentian and 

 Huronian drift. One of these measured 42 X 

 40 X 20 feet ; and as no rocks at all resembling 

 that of which these bowlders consist, or the 

 gneisses and granites of the Laurentian, occur 

 in the eastern ranges of the Rocky Mountains 

 (which are everywhere here continuous and 

 wall-like), there can be no doubt as to their 



eastern or north-eastern origin. As already 

 stated in my Boundary commission report, the 

 western margin of the region characterized by 

 Laurentian and Huronian drift is here about 

 seven hundred miles from the nearest part of 

 the Laurentian axis, and within a few miles 

 of the base of the Rocky Mountains. 



In the publications above alluded to, a num- ] 

 ber of cases have been instanced, of the great 

 elevations reached by erratics of eastern origin 

 in the western portion of the Great Plains. 

 The following additional examples from the 

 district now in question maj' be added. The 

 heights given are barometric, but have been 

 worked out bj' comparison with the U. S. sig- 

 nal-service observations at Fort Benton, and 

 may probably be depended on to within fifty 

 feet. At the summit of the high ridge crossed 

 bj^ the trail between Fort MacLeod and Pincher 

 Creek, Laurentian stones were found at an eleva- 

 tion of 4,390feet ; nearthe summit of the Rocky 

 Spring Ridge, on the trail from Benton to Mac- 

 Leod, and at several points about the intersec- 

 tion of the 49th parallel with the western 

 branch of Milk River (long. 113°), at eleva- 

 tions between 4,100 and 4,200 feet. On the 

 flanks of the W. Butte (lat. 49°, long. 111° 30') 

 Laurentian bowlders of small size, and pale 

 limestone resembling that of the Winnipeg 

 basin, are abundant at an elevation of 4,600 

 feet, while the highest actually observed frag- 

 ments attained an elevation of 4,660 feet. 



Evidence of the fact that glaciers of con- 

 siderable size debouched from the valleys of 

 the Rocky Mountain range is found in manj' 

 places. The grooving and fluting of the lime- 

 stone rocks near the efflux of the Bow River 

 from the mountains, and the moraines strewn 

 with bowlders of local origin near the mouth 

 of the South Kootanie Pass, and thence for 

 thirty miles or more northward along the base 

 of the range, may be speciall}' noted. 



In the foregoing notes no theoretical explana- 

 tions of the facts have been advanced. These 

 have been elsewhere discussed. In the publi- 

 cations above referred to, I was, I believe, the 

 first to define the so-called Missouri coteau as 

 one of the most gigantic monuments of the 

 glacial period of the continent, though argu- 

 ing against its formation as a moraine. In 

 whatever way the origin of the coteau may 

 eventually be decided, it is, however, well to 

 remember that it holds a position on the north- 

 ern plains scarcely more than midway between 

 the Laurentian axis and the western margin 

 of the Laurentian drift, and that the transport of 

 material to a much greater distance, and to 

 twice the altitude of the coteau region, has also 



