(17) 
or screw-stone of Parkinson.—Vol. 2. P. 15. Fig. 6. 
= These curious hollows are, not unfrequently, lined 
with calcareous formations, accompanied by perfect 
Quartz crystals, each quite distinct, the one from the 
other. But, the instances of meeting Quartz, in con- 
junction, or blended with the Lime, are not common, 
nor is the Quartz in. large quantities, 
