1864.] CHEMISTRY OF MANURES. 189 



conposition, and is penetrated in various directions by numerous 

 slender prisms of black cleavable pyroxene, sometimes half an inch 

 in len2;th. The layers of sedimentation are distinctly marked ia 

 this bed, as well as in the finer-grained si rata which enclose it ; 

 and the whole affords an interesting exaniple of the different eft'ects 

 of t!ie sainj agency upon beds of unli<e composition ; althou«;h it 

 would be impossible without comparative chemical analyses to de- 

 termine whether the siiicite which has here crystallized in the form 

 of pyroxene existed in thi unaltered sediment, or whether, as in the 

 case of the uncryst .Uized silicate from the altered limestone at 

 Montreal, it has been generated under the influence of the intru- 

 sive rock. In by far the greaternumberof cises, the only apparent 

 effect of the igneous rocks in the region under dev^cription upon 

 tiie p lias >zoic limestones and shales,has been a very local induration. 

 The appearance of crystals in these circumstances is a comparatively 

 rare occurence, and seems to depend upon conditions which are 

 exceptional, showing, as I have elsewhere leniaiked, that heat and 

 moisture are not the only condition of metamorphism. ^Siliiman's 

 Journal [2], xxxvi, 219.) 



With these few examples of local metamorphism I conclude the 

 present piper; proposing however to give in a subsequent one the 

 results of some investigations of certain indigenous crystalline rocks. 



Montreal, March 15, 1864. 



CHEMISTRY OF MANl KES.* 



CiNEREALf Constituents op Plants. — It is not however 

 exclusively by carbon, nitrogen, and the elements of water that 



* Continued from page 124. 

 f This term cinereal, from rme^gs, ashes, may ur ve convenient to indi- 

 <iate, withoui periphrasis, ih<^ash-constituenis of plants in contradistinc- 

 tion from their volatile elements. Some writers fall into the error of em- 

 ploying the epithet " mineral" to denote the asli-ingredients ; an error 

 in nomenclature probibly arising from some cm used impression that, 

 because of its earthy deprivation, the ash of piatiis is more mineral ia 

 character than the volatile or gaseous elemfiiis wliich air supplies and 

 firt' dissipates. The illustrious author of the min ral-theory seems, id 

 «ome of his earlier w.-iiings, himself to have counieiiatice.l this error. 

 Nevertheless, its simple indication suffices for itd refutation. Carbon and 



