284 GEOLOGY OF THE TfflRD DISTRICT. 



Onondaga limestone. This valuable building stone is coextensive with the Water-lime 

 group, but two interraptions to its course as to outcrop existing in the county ; one on Lime- 

 stone creek, the other at Onondaga valley. It is more free from flint in this county, than 

 further east. It is extensively quarried to the southwest of Syracuse, three quarries being 

 opened along the same range for the enlarged Erie canal. The rock is tough and hard, 

 requiring care in selecting such masses as are free from courses or parallel divisions caused 

 by shale, into which water may penetrate and freeze, and thus divide it into smaller parallel 

 parts. This is the only defect of this rock, which, however, is common to most stratified 

 masses ; but in this rock they are more numerous than in the base of the Trenton limestone, 

 as it exists on the Mohawk, or in the birdseye. 



This limestone makes first rate lime, but requires more. wood to bum a given measure ; 

 making a heavier lime, which not being sold by weight, the lighter limestones are preferred, 

 such as those of the Water-lime group. 



The Onondaga limestone forms a terrace in many parts of its range through the county. 

 The broadest is from Jamesville towards Onondaga valley, and along in the direction of the 

 quarries on the opposite side of the valley extending towards Nine-mile creek. It extends 

 up Onondaga valley, to where the road passes up the hill towards Lafayette. At Split-rock 

 there is a sink-hole in the rock, which passes down for about one hundred feet, and then by 

 an inclined opening into the valley below : the bottom and sides are said to be covered with 

 ice. This opening I did not see. 



North of Squire Brown's house, not far from Jamesville, there is a gulf in the water-lime 

 of over one hundred feet in depth. At the bottom of the gulf is a pond, the bottom of which, 

 it was said, was not reached by a line of one hundred and fifty feet in length. The Onondaga 

 limestone forms the surface rock above the gulf. 



The Corniferous limestone is exposed upon the Onondaga in many parts of the range, from 

 the east to the west end ; namely, near Manlius square, the road from Fayette to Pompey 

 hill, both sides of Jamesville, Spht-rock, Marcellus, and Skaneateles outlet. But little of it 

 is quarried or used. 



The Seneca limestone is abundant in the county, and many favorable points are presented 

 for examination ; such as along the side-hill at West hill, the quarry at Marcellus, the road 

 by Jamesville, etc. 



Marcellus shales. There is a greater thickness of these shales in this county than in any 

 of the others ; they are tolerably well exposed near Marcellus, and are seen in innumerable 

 places upon the high ridge from east to west through the county. The lower division is met 

 with at several points, showing its fossils, and excavations in various places have been made 

 for coal. The lower division is best exposed along the road to the west of Manlius square, 

 and in the quarry and along the small valley of the quarry towards Onondaga valley. Through- 

 out they form the base of the next group ; between which and the present, no well defined 

 line of division has yet been observed, but the fossil character shows a difference between the 

 groups. 



