NIAGARA FALLS AND VICINITY 99 



shanties on the railroad, where the top of the Clinton limestone is 

 on a level with the roadbed, this rock was formerly quarried on the 

 river side, and here a good opportunity is afforded to collect fossils 

 from the limestone fragments. Blocks of the various limestones 

 are also seen by the side of the track between the second and third 

 shanties. 



At the whirlpool on the Canadian side the Clinton limestones 

 are seen in both banks of the old St Davids gorge, the section on 

 the west showing glacial striae. Near the foot of the eastern wall 

 of this old gorge and on the talus heaps which flank it, are large 

 masses of calcareous tufa often inclosing leaves, moss or other vege- 

 table structures. These masses appear to come from the horizon 

 of the Clinton limestone, though they have not been seen in place, 

 and it is not improbable that a " petrifying spring " carrying a 

 strong solution of carbonate of lime issues from this rock. Springs 

 issue abundantly from between the two members of the Clinton 

 limestone, and they carry lime in solution, as is indicated by the 

 deposit of soft calcareous ooze on the rocks and other substances 

 over which this water flows. On exposure to the atmosphere this 

 ooze will dry and harden. The joint faces of the Clinton limestone 

 are everywhere veneered over with a thin deposit of calcium car- 

 bonate. 



Limestone lenses of the Clinton. At intervals in the upper Clinton 

 limestone may be seen large lenticular masses of a compact, hard 

 and apparently structureless limestone, often concretionary and not 

 infrequently showing numerous smooth and striated surfaces of the 

 type known as " slickensides " and which are indicative of shearing 

 movements. One of these masses is visible in the bank opposite 

 the third watchman's hut. Its greatest thickness is about 8 feet, 

 and it lies between the upper limestone and the overlying shale, 

 being partly embedded in both. The rock is often cavernous or 

 geodiferous, the cavities when freshly broken being filled by snowy 

 gypsum or grayish anhydrite. Fossils are abundant in this rock. 



Several other lenses of this type are visible in the upper Clinton 

 limestone where it is crossed by the Rome, Watertown and Ogdens- 

 burg railroad below Lewiston hights. These masses are however 



