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PKOCEEDINGS OP THE GEOLOGICAL SOCIETY. 



[Apr. 10, 



line would then leave the Kocky Mountains in latitude 56° N., 

 near Peace River, and would follow what is now the water-shed 

 between the Saskatchewan and the rivers more to the north, till it 

 reached the 107th of longitude. Prom this point the Thickwood 

 Hills, Eagle Hills, and Thunder-breeding Hills would form the 

 headlands of a great bay into which poised the waters of the two 

 Saskatchewans, at that time independent rivers debouching where 

 they now make the acute bends known as their " Elbows". The coast- 

 line was then continued to the south-east, forming the coteau that dips 

 between the Missouri and St. Peter's Pavers. As seen from a dis- 

 tance when travelling in the low plains, this great steppe appears as 

 a range of blue hills with a smooth undulating outline. On ap- 

 proaching it a gentle ascent is accomplished for many miles, after 

 which an abrupt rise of from 400 to 600 feet has to be effected, 

 generally in from 4 to 6 miles. The surface of the slope is extremely 

 rugged, and has evidently been worn into pot-holes, ridges, and 

 conical mounds by the action of water on the soft clay strata of the 

 Cretaceous group. Everywhere the slope is thickly strewn with 

 boulders, all derived from the Laurentian chain to the east, or from 

 tho Bird's-eye Limestone which rests on the western flank of that 

 axis. 



Near the elbow of the North Saskatchewan a remarkable group of 

 boulders of this kind of limestone, of enormous size, crosses the 

 country in a line parallel with the coteau to the west. This line 

 has been observed at points 30 and 40 miles apart. They occur as 

 great angular masses, consisting of several of the beds of limestone, 

 the coherence of which being very slight proves that they must have 

 been stranded without any great violence. One of these masses con- 

 tains over 3000 cubic feet of stone, and rests on the plain obliquely 

 with its south-western angle buried in the soil (see sketch, fig. 2). 



Fig. 2. — Boulder on the Plains south of Carlton. 



More to the west than this is a line of sand-hills, which has evi- 

 dently marked a coast-line, although their original position may now 

 bo much altered, since they are still wind-blown as during their 

 first production. They have a clear relation to the ancient level, 

 and are found at the same altitude over such a stretch of country, 

 always at a little distance from the base of the escarpment, that there 



