15ti HELDERBERG DIVISION. 



Localities where it may be observed. Though this rock may exist in Oneida county, yet it 

 is too obscure, of loo much concealed in its own, or in the debris of other rocks, to at- 

 tnct much attention. 



In Camillus, at the railroad cut , is one of the best localities for studying' this division of 

 tlic group. The place is weal of Camillus village, and can not fail to attract the attention 

 of travellers ove* this line of conveyance. More than one hundred feet of it is exposed, 

 and in all the conditions and with all the products of which I have spoken, except that the 

 ted rock is not exposed or does not exist at this place. 



Another locality of interest, is about three miles east of Manlius centre, at the Green 

 lakes, where the superior part of this division exists with massive beds of plaster. This is 

 superior to the rock at the deep railroad cut in Camillus. The limestone shale at the lakes 

 is thin-bedded and fragile, but not so much so as the mass below. 



At Cayuga bridge, the same series is exposed in the banks, where many oven-shaped 

 cavities exist, from which plaster has been extracted, or from which it has been dissolved 

 by water percolating through the strata. 



The lower mass exists still farther west, in the vicinity of Lyons, Newark and Lockville : 

 at the latter place, the locks for the enlarged canal are excavated in it. Westward beyond 

 the Genesee river, it is exposed in Byron and Alabama ; and at Bergen centre, the railroad 

 rims near the excavation for plaster. At Palmyra, it is upon the banks of the canal. In 

 Erie county, the beds are concealed by thick beds of drift. Some few excavations expose 

 it sufficiently to prove its continuation. 



Fig. 26. 

 Section illustrating the position of the lakes, with the vermicular limerock of Eaton, or porous limestone. 



a. Canal, b. Green lakes, sometimes called Lake Sodom, e. Porous limestone : plaster beds above. T. Manlius 

 village. The section extends south three miles, passing over the formation embracing the plaster beds ; the 

 highest strata are the watcrlime layers on the slope of the hill. The hill intervening between the Green lakes 

 is traversed by fissures, through which most of the water percolates unul it reaches the more impervious strata, 

 the green shales. The water of the Green lakes (of which there are two) is unpleasant, or rather bitter ; con- 

 tains a great amount of lime : every twig or stick which happens to fall into it becomes incrusted with carbonate 

 of lime. They are situated on small but deep depressions or basins, which, unlike many others in the surround- 

 ing country, are not formed by drift currents, or by streams that have mechanically worn them out ; neither are 

 they produced by fractures or uplifts, as the strata are undisturbed. To what cause is to be attributed the basin- 

 shaped depressions in which these lakes are contained, is a matter of speculation, that has not as yet been satis- 

 factorily determined. 



A general staff ment of the extent of this division of the Onondaga-salt group. Beginning 

 as heretofore, at the east, we find the green shales and gypseous rock first appearing in 

 Oneida county, near Vernon village, where, as is stated by Mr. Vanuxem, the constituents 



