188 Agricultural Geology of Onondaga County. [April, 



huge potash kettle are cultivated frequently to their tops. In some 

 instances we find the surface in an inverted position to the one 

 we have alluded to — conical excavations, or excavations in the 

 shape of the inside of a potash kettle. The bottoms of those are 

 usually perforated ; the waters which flow down the inside slopes 

 leak out and pass through the strata which form the bottom. 

 Tufa usually accumulates upon all the slopes where water flows, 

 and trees, leaves and twigs are every where petrified in these 

 deposits. 



These conical depressions, however, are not always perforated, 

 they sometimes hold water, as in the case of the Green lakes, 

 which are quite deep, as is found by soundings. Section 2 illus- 

 trates the peculiar topograpy of this part of the county. 



fig. 2. 



b, one of the Green lakes, which is more than 300 feet deep. T, tufa 

 beds, which accumulate on the slopes of the hills, a, green shales, c, ver- 

 micular lime rock, d, hydrarlic limestone. 



The basins which contain these small lakes may have been 

 formed by the removal of soluble matter, in the first place, and 

 may have been only a sink hole, but has been gradually enlarged 

 and deepened by the instrumentality of water, as a solvent, and 

 as a mechanical agent in breaking down and removing the soft 

 materials of which the sides of the basin are composed. 



The county south of the Erie canal rises into rounded hills. 

 Those on a near inspection are formed by successive terraces, 

 more or less distinct, but usually rather limited. The effects of 

 streams upon those materials are worthy of notice, they frequently 

 insulate a section of country of three or four- miles square. The 

 important effects which follow from this insulation is, that all the 

 superior part is perfectly drained, and all the the surface water 

 flows out at the low levels, or at the place where the thin bedded 

 limestones meet the comparatively impervious shales. Here 



