242 



GEOLOGY OF THE TfflRD DISTRICT. 



77. 



Skmcing a transverse section of the ancient valley and the prciaU lake. 



A tran8\'erse or ejisl and west section of the reservoir, as in the wood-cut above, would show 

 the red shale aa, forming the sides and bottom of the ancient valley ; the valley b, filled up 

 with alluvial ; c, the Une of lake marl ; d, Onondaga lake, being a part of the valley not filled 

 with stony or earthy materials. 



Lake Sodom. 



This lake is small, but of peculiar interest from its great depth, circular form, depositing 

 marl, and from its waters near the bottom being highly charged with sulphuretted hydrogen. 

 Its greatest depth is 168 feet. It is excavated in the lower part of the second deposit of the 

 Onondaga salt group, and the red shale below that deposit. For further particulars, the reader 

 is referred to the Report of 1839. This lake is of importance in showing that deep excava- 

 tions exist along the range of the gypseous deposit, and that the deep excavation of Onondaga 

 valley is not an anomalous one 



