Boulders Due to Rock Decoy. — Cf^lnnii. 373 
Abundant supplies of drift Ijoulders from a relatively small 
exposed tract of the bed rock, resulting^ mainly, as vvc may 
suppose, from preglacial weathering and favorable joint struc- 
ture, are illustrated in the farthest known transportation of 
rock fragments in the drift of North America, from James 
bay southwest to North Dakota and Minnesota, as recorded in 
part by Dr. Robert Bell, of the Canadian (ieological Survey, 
whose observations are supplemented by my own. The rock 
thus recognized is a "dark grey, granular, siliceous felsite or 
grey waeke. .. .characterized by roiuul s])nts, from the size of 
a pea to that of a cricket ball or larger, of a lighter cf>lor than 
the rest of the rock, which weather out into jiits of the same 
form." It occurs //; .s-/7;/, as reported by Dr. Ik'U, on Long 
island, off Cape Jones, on the east coast of Iludson bay, where 
it is narrowed to form James bay, having there a southwest- 
ward strike, and proljablv continuing un<ler the sea for some 
distance in that direction. He notes that the abundance of 
pebbles and boulders of this rock is the most remarkable fea- 
ture of the drift on the west coast of James bay and along the 
Attawapishkat, Albany, and Kenogami rivers, and that its 
fragments have bt.en found by him as far west as Lonely lake, 
and southward to lake Superior.*. 
Farther to the southwest and south, I have observed frag- 
ments of it. usually only a few inches, but in some instances 
a foot or more in diameter, occurring very rarely in the drift 
in the northeastern part of North Dakota, where the largest 
piece ever found l\v me was about thirty miles south of the 
international boundary and fifty miles west of the Red river, 
and at numerous localities in ^linnesota, where it extends at 
least as far south as Steele county, seventy-five miles south 
of St. Paul, and a thousand miles southwest of its outcrop 
north of James ba\'. i 
Another illustration of very extraordinary boulder sup- 
plies, doubtless explainable as here indicated, is seen on a tract 
of a few square miles close eastward of the Fabyan House in 
the White mountains of New Hampshire, where granite boul- 
ders, including many of great size, derived from the contig- 
* GeoJ. and Xat. Hist Surver of Cfinailn. Anntinl Renort. new •piir^. vol. 
ii, for 1886, p. SOO; compare Report of Progrecs for 1878-79, pp '-■2. 2.^C. 
t Geo/, nnrl .V<it. Hist. Surrey of Minncsotn. Twenty-second Anniwil Re- 
port, tor 1893, pp. 33-34. 
