228 EDWARD B. MATHEWS 
Although the gold ores and the fluorite are sometimes inti- 
mately associated in the mining area near Cripple Creek, no indi- 
cations of gold, sulphides, or tellurides were seen in any of the 
sections of the Summit type. 
Distribution.—TVhe rocks of the Summit type are confined to 
a small area about the Summit and down the western slope of 
the highest part of Pikes Peak, and the relation between them 
and the other granites is only seen in a few places. On the main 
peak there seems to be a system of radiating dikes, but the con- 
tacts are not well exposed in place. In Wilson Creek canyon 
and near the intersection of Spring Creek with the Cripple 
Creek-Florissant road there are dikes of granites correlated with 
that of the Summit type which clearly cut the older Pikes Peak 
granite. 
Towards the other granites this type seems to be older, since 
it is never found in them, while they occur in small masses within 
its areas. 
Weathering —In the manner of their weathering the rocks of 
the Summit type show many differences from those of the Pikes 
Peak type. Instead of disintegrating into massive, rounded 
bowlders and coarse gravels like the latter, the granite-porphyry 
breaks up into smaller angular blocks, as illustrated in the 
familiar views of the Upper Station of the Pikes Peak Railway. 
These blocks and many of the ledge exposures, moreover, have 
a glazed crust similar to that observed on bowlders of the Pikes 
Peak type. What the nature of the process is which produces this 
surface was not determined in the somewhat hasty survey of the 
upper portions of the mountain, although the natural surround- 
ings suggest three possible agencies for such polishing, viz., 
blown sand, ice, and chemical action. The smoothness of the 
surfaces and the occurrence of polished surfaces in sheltered 
hollows is against any polishing by sand, while the presence of 
a crust on somewhat recently formed bowlders and steep slopes, 
and the absence of glacial striae militate against any explanation 
based on ice action. The thickness of the shell and the decayed 
character of the interior, on the other hand, seem to indicate that 
