CLIMATES OF GEOLOGIC TIME—SCHUCHERT. 287 
In western Sutherland and Ross, Giekie states that the observant 
traveler must be struck by the ‘‘extraordinary contour presented by 
the gneiss. A very slight examination shows that every dome and 
boss of rock is ice worn. The smoothed, polished, and striated sur- 
face left by the ice of the glacial period is everywhere to be recognized. 
Each hummock of gneiss is a more or less perfect roche moutonnée. 
Perched blocks are strewn over the ground by thousands. Jn short, 
there can hardly be anywhere else in Britain a more thoroughly typical 
piece of glaciation” (1880). 
Over this eroded and smoothed ground was formed a coarse reddish 
breccia with many of the stones decidedly angular and ‘‘sometimes 
stuck on end in the mass.” Some blocks are ‘‘fully 5 feet long” but 
none were found to be scratched or striated. The breccia ‘‘is quite 
comparable to moraine stuff.’””’ The material came from a land that 
lay to the northwest and that has since sunk into the Atlantic. 
EARLIEST PROTEROZOIC GLACIATION. 
Canada.—The oldest known tillite was recently described by Prof. 
Coleman. (See fig. 3.) It occurs at the base of the Lower Huronian 
in the so-called ‘‘slate conglomerate,” and therefore near the base of 
the geologic columm accessible to geologists. These conglomerates 
are found ‘‘from point to point across all northern Ontario, a distance 
of nearly 800 miles [now placed at 1,000 miles] and from the north 
shore of Lake Huron in latitude 46° to Lake Nipigon in latitude 50° 
[now placed at 750 miles].” ‘‘The appearance of these so-called 
slate or graywacke conglomerates is closely like that of the Dwyka 
bowlder clays of Africa” (1907). They rest on various formations 
older than the Huronian, an ‘‘undulating surface of low hills and 
valleys, the conglomerate often more or less filling in these valleys.” 
A scratched or polished underground has been found in three places, 
but as a rule such are not seen because of the unfavorable conditions 
for their display. The evidence of the tillites is in favor of the view 
that glaciation in Huronian Canada was not ‘‘the work of merely 
local mountain glaciers,” but rather due to ‘‘the presence of ice 
sheets comparable to those which formed the Dwyka. * * * 
This implies that the climates of the earlier parts of the world’s history 
were no warmer than those of later times, and that in Lower Huronian 
times the earth’s interior heat was not sufficient to prevent the for- 
mation of a great ice sheet in latitude 46°.” 
CLIMATIC EVIDENCE OF THE SEDIMENTS. 
During the past 10 years it has become evident that the color of 
the delta deposits of geologic time, and especially that of continental 
deposits, is to be connected largely with differences in climate. 
