134 
thinning out to %4 inch of an inch on the north bank and probably 
doing the same toward the south. This end was covered with 
detritus and not observable. 
Dixk III. About a foot east of No. 2, a third dike was 
observed, visible only for about two feet near the center of the bed 
of the stream. The ends were covered with detritus. It is par- 
allel to the others and is not more than 1% inches in thickness. 
The strike of these dikes would seem to indicate that they are the 
continuation of the series near the third falls in the Townley 
ravine. No traces of the first series near the Tully Limestone 
could be found. It is quite possible that these were the dikes 
noticed by Kemp, as they correspond to his descriptions in the 
paper quoted.* 
The large ravine, which cuts through the Hamilton shales 
just south of the last mentioned gorge, did not reveal any trace 
of the dikes. It probably does not extend far enough to the east- 
ward to expose them. 
A visit was also made to Ithaca, ten miles south of Ludlow- 
ville, where the dikes are also exposed. The locality studied was 
in the gorge of Cascadilla Creek, between the entrance to the 
Cornell campus and the street car trestle. 
Dike I. occurs between the trestle and the new bridge over 
the creek. It forms a noticeable depression in the rocky walls of 
the creek but is difficult to study because the water from the race- 
way of the reservoir follows this depression in its descent to the 
creek. ‘This has succeeded in eroding a larger channel for itself 
than the natural width of the dike and prevents access to the 
same. In places, pieces of the comparatively hard dike rock can 
be broken off through the dashing water, and these show it to be 
a peridotite of dark green color with numerous crystals of olivene. 
In general appearance it closely resembles the Syracuse ser- 
pentine. Owing to the peculiar conditions, it was impossible to 
tell the exact width of the dike but it could not have been more 
than 28 or 30 inches thick. ‘The adjoining sandy shales of the 
Portage group have weathered down with the dike, and been 
eroded by the stream, so that the depression in which the dike 
*Amer. Jour. Sci., Nov., 1891, p. 410. 
