64 QUARTERLY JOURNAL. 



another element of corals, and as many limestones are magnesian, 

 it is inferred that these limestones have also a similar origin. Pro- 

 ceeding still farther, Mr. Dana infers that the magnesian minerals, 

 as serpentine, steatite, pyroxene, tremolite, spinelle, chrondrodite, 

 all have a similar origin ; a derivation from organic matter. But now 

 let us enquire, are these generalizations necessary 1 Are they pro- 

 bable ] 1. As it regards the phosphate of lime, we have given 

 two localities [p. 60,61,] where it forms the gangue of iron ores ; 

 and again it exists in gneiss, mica slate and granite. Is it of organic 

 orio-in here ? There is no proof of it. It is only when contained in 

 limestones that phosphate of lime and magnesia are supposed to 

 have this origin. The question must turn then, on this point : are 

 the relations of these limestones in St. Lawrence, Jefferson, Essex, 

 and Orange counties, such as to bear out and sustain the hypothesis 1 

 We answer in the negative, and would add in support of our ne- 

 gative, their relations are such as to overthrow — to entirely over- 

 throw it — to demolish it. The limestones which are richest in 

 phosphate of lime and other magnesian minerals, are universally 

 enclosed in gneiss or granite — they are in veins or beds ; one in 

 particular, which is rich in these minerals, projects out of the hy- 

 persthene rock, or comes up from below. How a sedimentary, 

 coraline rock could get into this position remains to be shown. That 

 it has been acted upon by heat is not denied, but that this and 

 many other masses like unto it were originally sedimentary rocks, 

 not a fact in existence has ever been cbserv£d to sustain the hy- 

 pothesis. Again, the magnesian limestones of Berkshire county, 

 the Stockbridge limestone, which is truly a sedimentary rock and 

 stratified, has never furnished to my knowledge a crystal of phos- 

 phate. It is here that we ought to find it, inasmuch as it is gran- 

 ular or crystalline, and may have been formed at a period when 

 animals dwelt in the seas upon whose bottom it was deposited. 

 But once more and we shall drop the subject. We wish to be un- 

 derstood not to deny the possibility of changes of the kind Mr. 

 Dana speaks of. We deny the propriety of the application he has 

 made of the facts to the limestones of the counties mentioned 

 above. For a full account of this origin we refer the reader to the 

 Geological Report of the 2d District. 



