*298 
GEOLOGY OF THE THIRD DISTRICT. 
appear to accompany the particles of limestone in all the upper rocks, the carbonate of iron 
being in considerable quantity at the upper part of the Catskill group, and under the coal 
deposit in the neighborhood of Ralston in Lycoming county, Pennsylvania; and it is there 
worked, affording the purest of iron. 
14. Tompkins Countv. 
The east half of this county, embracing the towns of Lansing, Groton, Dryden, Caroline, 
Danby and the east half of Ithaca, belong to the third district, the county being divided 
between this and the fourth district. 
The lowest rocks of this portion of the county are those of the Hamilton group; but they 
are only to be met with along Cayuga lake, commencing at the north end of the county, and 
continuing up the lake to near Bloom’s lime-kiln, below which they disappear under the Tully 
limestone and the lake. They are well exposed along the creek at Ludlowville, disappearing 
also under the same rock at the falls in the creek, and the ravines near the village. 
The Tully limestone is the next rock in succession. It is also seen in the same range of 
country, being well exposed along the lake, and readily traced from the county line to the 
kiln, where it was quarried and burnt for lime. Along the shore in many places are nume¬ 
rous large blocks of the rock, which have fallen from the cliff, owing to the removal of the 
soft shale beneath it upon which it rested. Blocks of this rock have been transported many 
miles south of the head of the lake, along the high grounds of the Cayuta and Six-mile creeks, 
and are quarried for lime; also on the road to Dryden, three or more hundred feet above the 
lake. 
The Genesee slate , the common associate of the limestone, also appears on the same side 
of the county, ranging with the two lower masses, and showing a greater extent of surface, 
as may be seen along Salmon creek ; and extending up the creek from the falls over the Tully 
rock, as well as in some of its other branches, the south one for example, where it forms two 
falls. 
Portage and Ithaca groups. These groups cover the remaining part of the town of Lansing^ 
the whole of Groton, the northwest half of Dryden, and the southwest part of Ithaca. The 
lowest layer along the lake is a hard solid sandstone of variable thickness, some parts about 
four feet, being the maximum. They show at Falls creek, Cascadilla creek, the Inclined 
plane, and at McCormick’s quarry, some good building stone ; but the great mass consists of 
rather hard and coarse shale, some quite slaty. Though the shale is somewhat enduring in 
the mass, when the edges merely are exposed, as is obvious in the cliffs along the lake, and 
at the falls of the creeks near Ithaca, the Inclined plane, etc., yet it is but a perishable mate¬ 
rial when otherwise exposed. 
Chemung group. In the present state in which this group is placed, but little need be said, 
especially as it must occupy but a very small part of the east half of the county. Considering 
it to commence towards the upper part of the Inclined plane, no change whatever was noticed 
