128 



objections adduces the occurrence of apatite in iron ore, and in gneiss, 

 mica-slate, and granite ; in which we have, at least, no evidence that 

 these organic structures have existed. Again, the limestones which 

 are the richest in phosphate of lime, are always enclosed in granite or 

 gneiss. Amer. Quart. Jour., i. p. 63, 64. 



These objections seem to me to be valid. I can see no reason why 

 phosphate of lime, in the form of apatite, may not be an original pro- 

 duct, as well as fluor spar, or the magnetic iron ore itself. It is an 

 overstrained view, to refer the formation of every mineral to chemical 

 action exerted upon some previously existing body. And after all, it 

 only removes the difficulty in regard to the formation of these sub- 

 stances one step further, for it may be fairly asked, whence the phos- 

 phate of lime in the coral was derived ? 



FLOUR SPAR. 



(Mineralogy of New- York, page 243.) 



I have only to add the occurrence of this mineral in small quantities 

 in Gouverneur, St. Lawrence county, reported by Dr. Emmons, and 

 which had escaped my notice in the explorations which I made in that 

 county. See Rep. on the Geol. 2d Dist. p. 366. t 



I may also state, as connected with the general history of this mine- 

 ral, that it has been found in many of our common waters, and that its 

 existence in recent and fossil bones, has been attributed to this source. 

 See the papers of J. Middleton, Esq., and of Dr. Daubeny, (Lon. Ed., 

 and Dub. Phil. Mag., vol. xxv, p. 14 and 122.) 



HYDRAULIC LIMESTONE. 

 (Mineralogy of New- York, page 256.) 



Dr. C. T. Jackson's analysis of the Rosendale hydraulic limestone and 

 cement, will be found in the Trans, of the Amer. Ass. of Geologists, 

 for 1845, p. 48. 



The following fact, noticed by Bezelius, throws some light upon the 

 chemical nature of hydraulic limestones : " When muriatic acid is ad- 

 ded to hydraulic mortar, which has been under water three months and 

 reduced to powder, it gelatinizes at the end of a few minutes. -Hence 

 it is inferred that there is formed a double silicate of lime and alumina, 

 a native zeolite, which gives solidity to the mortar." Berzelius % Ann. 

 Report for 1844. 



