wt _ 
ea, 
94 © Erratic Phenomena about Lake Superior. © me, 
before spreading again more. uniformly beyond its limits. To the: 
oscillations of the whole mass in its southerly movement, ac-)_ 
cording to the inequalities of the surfaces, we must ascribe the — 
 crossfng of the straight lines at acute angles, as we observe also 
at the present day under the glaciers, as they swell and subside, 
and hence meet with higher aud lower obstacles in their irregular 
course between the Alpine valleys. 
n deep? narrow chasms, however, we find now and then great- 
er deviatioys fr6m the normal direction of the striae, where con- 
siderable masseg of ice could accumulate, and move between score i 
walls under a lateral pressure of the masses moving onwards from 
the north. Such a chasm is seen between Spar jsland and the 
main land opposite Prince’s Location, south of Fort William, .. 
where the furrows and scratches run nearly east and west. But 
here also, there is no tumultuous disturbance in the continuation 
of the phenomena, such as would occur if icebergs were floate 
and stranded against the southern barrier. he same continuity 
of even, polished surfaces, with their scratches and furrows, pre- 
vails here as elsewhere. The angles which these scratches form 
with each other are very acute, generally not exceeding 10°; but 
at times they diverge more, forming angles of 15°, 20° and. 25°. 
In a few instances, I have even found localities where they cross- 
ed each other at angles of no less than 30°; but these are rare 
exceptions. It may sometimes be noticed that the lines running 
in one direction form a system by themselves, varying very little 
with each other. At ot r times, a sy ster of lines, strongly 
marked and diverging sim catighalys seem to pass over another 
system, in which the lines form various angles with each other. 
Again, there are places,—and this is the most common case,— 
where the lines diverge slightly, following, however, generally 
one main direction, which is crossed by fewer lines, forming more 
open angles, These. differences, no doubt, indicate various oscil- 
lations in the movement of the mass which produced the lines, 
and show probably its successive action, with more or less in- 
tensity, upon the same point at successive periods, in accordance 
with the direction of the moving force at each interval. The 
same variations within precisely the same limits may be noticed 
in our day on the margin of the glaciers produced by the increase 
or diminution of the —_ of their mass, and the changes in the 
rate of their moveme 
The loose aiaerate which produced, in their onward move- 
ment under the pressure force, such polishing and grooving, con- 
sisted of various sized boulders, pebbles and gravels, down to the 
most minute sand and loamy powder. Accumulations of such 
are found everywhere upon these smooth surfaces, and 
