No. 3.] SPENCER — PALAEOZOIC GEOLOGY. 161 



with (and repl.icing accordin<r to Sorby) a portion of the cal- 

 careous sand derived from the organic remains in this reirion, 

 have probably in a jireat dcurce given rise to our Nia<2;ara lime- 

 stones, all of vviiich are more or less of the character of true 

 dolomites, but where some contain mechanical detritus as silice- 

 ous and ai-gillaceous mud. 



From this examination of the character of the limestones of the 

 Ni--io:ara group, it is not surprising that tliere is such a paucity of 

 fossils in this great development of rocks so largely composed of 

 their remains. In very many strata T have found no fossils what- 

 ever, and even in those where tliey are most abundant, one is 

 rewarded only after a long patient searcli. Yet, with all these 

 difficulties, the geologist may collect in the region of our study a 

 large number of species, of whicli there are catalogues under 

 those parts of this piper on tlie Medina and Clinton epochs, 

 and a still larger list at the end of this portion of the paper on 

 the Niagara epoch proper. 



VII. — MINERALS OCCURRING IN THE NIAGARA GROUP. 



Excepting the beds of stone fit for building purposes and for 

 burning to lime, there are no minerals about the western end of 

 Lake Ontirio of economic importance. However, many years 

 ago some futile attempts were made south of the village of Beams- 

 ville to work a small "find" of gahHia. The only sandstones fit 

 for building purposes is the '• Gray band "' of the Medina forma- 

 tion. Blocks of this stone of r.my dimension that can be handled 

 are obtainable. This stone has been extensively worked at 

 Dundas, ILimilton, Grimsby and Beamsville. A great draw- 

 back in quarrying this material is that it can only be procured 

 along the edge of the escarpment, and requires a vast amount of 

 the shaly rocks of the Clinton formation to be removed, and 

 even tlicn tlie supply is of a limited quantity. Tiie stone is very 

 touiih and hard on tools. I am infn-nied that this rock was 

 formerly manufictured intu grindstones. The majority of the 

 beds of limestone aie too thin, or inferior, for anything more 

 than the lougliest building material. However, there is a suffi- 

 cient number of layers to supply an abundance of building mate- 

 rial of which the handsomest is obtained from the ureat dolomite 

 (No. 8) and the subjacent beds. In fact all the beds belonging 

 to the Ni.igara series, that will at all admit of use, are quarried 

 at Hamilton, and the broken material of the "Chert band" and 

 Vol. X. L No. 3. 



