
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS. 221 
Long River, but not so clearly. Atone place 20 to 30 feet of drift forms a 
vertical cliff. Boulders are abundant in the bed of the stream, and 
appear to be chiefly Laurentian. 
505. In order to ascertain as far as possible, the origin of the foreign 
material of the drift, and the relative proportions of its various consti- 
tuents, the following method was adopted. An average collection of peb- 
bles, taken at random from the gravel of any locality, was made; stones 
above or below a certain size being rejected for convenience, and care 
being taken where possible, to combine gatherings from two or three 
spots for each locality, and to make the collection a large one. The 
pebbles so obtained, were then carefully enumerated, and divided litho- 
logically into groups, which were referred as far as possible to their 
formations. From the numbers thus obtained, percentage ratios have 
been calculated. The comparative simplicity of the geological features of 
the interior of the continent, the similarity of the lithological characters 
of the formations over great areas, and the absence of harder meta- 
morphic rocks in the strata of the plains; are specially favourable to such 
an investigation, and the results serve to show the general course of the 
drift in a region where rock surfaces capable of preserving glacial strie 
are entirely absent. It was at first intended, to enumerate the boulders 
and larger erratics in this way, but the criterion by smaller pebbles was 
found more frequently applicable, and wherever comparison was possible, 
the result obtained from them appeared to agree closely with the pro- 
portional importance of the larger masses. In one respect, the informa- 
tion to be derived from the smaller constituents of the drift, is more trust- 
‘worthy than from the larger, as the limestone suffers rapidly from frost 
and weather, breaking down and ceasing to occupy a prominent position 
among the boulders of harder metamorphic rocks. Particular attention 
was, however, given to the larger erratics also, and it is hoped that infor- 
mation derived from different parts of an east and west line, over 800 
miles in length, across the central portion of the continent, may not be 
unimportant. 
506. The first numerical examination was made on the Line about 
eighteen miles east of the present western boundary of Manitoba, with 
the following result :— 
1. White limestone, of the ordinary kind.................... 48.18 
2. Granitic and gneissic rocks, generally pinkish.............. 38.48 
ee ES ere eR ea ee ats ay e Wh'e atly a'n'b eg o'a's:s alphas" o's 1,22 
4. Pebbles, chiefly or entirely of crystalline quartz.......... 9.75 
a PRR Py ee ee ee ee 2.43 
6. Dark coloured, hard, coe ey a | Ne ea 4.87 
7. Soft reddish decomposed rock. ..............c0e00cceeeee 1,22 
8. Grey rock ; probably fragments of Cretaceous nodules. .. 1.22 
