56 REPORT OF THE 



from its oeeurrence on the Niagara river. It reaches here an 

 elevation of nearly 109 feet above the lake, and dipping- 

 southward sinks beneath the water on the south shore of 

 the island. This assemblage of strata embraces a band five 

 feet thick of highly arenaceous limestone, at bottom, overlain by 

 seven feet of a hard, gray crystalline limestone, which furnishes 

 an excellent quality of quicklime. This is overlain by for/y- 

 five feet of a rough, crystalline, geodiferous limestone, followed 

 upward by eight feet of broken thin-bedded limestone, and six 

 feet of rough vesicular limestone. The white, massive, marble 

 like, magnesian limestone, twenty feet thick, occupying the 

 south shore of the island, is still higher ; and the series is com- 

 pleted by about six feet of thin bedded brown limestone, 

 abounding in Favosites niagarensis, Halysites escharoides, Helio- 

 lites spinipora, &c. The thicker masses are eminently charac- 

 terized by Pentameri, while not one has been found in the Clin- 

 ton Group. The total observed and measured thickness of 

 these rocks does not exceed one hundred feet, and it is doubtful 

 whether the dip of the strata across Drummond's Island would 

 give them a calculated thickness much greater. The rocks 

 which emerge from the water on the south side, preserve a 

 gentle and pretty uniform rise to the top of the escarpment at 

 Marblehead, and west of there. Only the uppermost, thin- 

 bedded layers seen on the south shore, are wanting at Marble- 

 head. - 



The economical qualities of this limestone, so far as I am 

 aware, have not been reliably tested. The large per centage 

 of carbonate of magnesia contained in the heavier beds, renders 

 them a pretty well characterized dolomite. According to the 

 researches of Vicat, this proportion of carbonate of magnesia, 

 mixed with about 40 parts of carbonate of lime, possesses 

 -hydraulic properties; and only a few hundredths of clay are 

 required to be added, to produce the strongest hydraulic cement. 

 It is not at all unlikely that somewhere upon the shores of 

 Drummond's Island a good hydraulic limestone may be found 

 compounded by the hand of natuie. 



