222 CALCAREOUS MANURES-APPENDIX. 



Prof. Wm. B. Rogers found in the green-sand of Virginia- 

 Silica 51.70 



Piotoxido of iron - - - 25.20 



Pot;\.<^sa ..... 10.33 



Water .... 10. 



Magnesia, a trace. 



97.23* 



The foregoing mr.y be falcon as a fair exhibition of the compo.-ition of the green par- 

 liclfs in green-sai;d ; anil the following analj'sns may serve to show the constitution of 

 such cliloiites .-.nd mica as may be presumed to be most analogous totlie green substances 

 in the earth under consideration. 

 M. Vauqueliu found in the green-earth of Verona — 



Silica . - ... . 52.00 



Ma2;nesia .... 6.00 



Alumina - . . - . 7.00 



Protoxide of iron - - - 23.00 



Pofassa ... - - 7.50 



Water - - - - 4.C0 



99.50t 

 Dr. Thomson found in the chlorite-earth, from the highlands of Scotland — 

 Silica ..... 43.166 

 Magnesia .... 2.916 



Alumina .... 16851 



Oxide of iron . - - I9.ri()-D 



Potassa ..... 6.553 



Lime .... 2.675 



Water . - . . . 2.350 



98.7I8J 

 The composition of the most common silvery mica from Zinwald (Bohemia) was 

 ascertained by M. Klaproth to be the following — 



Silica . - ... .47. 



Alumina .... 20. 



Pofassa - - . - - 14.50 



Ox. iron .... 15.50 



Ox. manganese .... 1.75 



98.7o§ 

 Having described the grounds on which I arrive at the conclusion that the green grains 

 of this earth are chlorite, or chlorite blended with mica, and rarely specks of serpen- 

 tine, I cannot but express the opinion, that as a nutritive manure the efficacy of the 

 green particles has been greatly overrated. As these particles are very little liable to 

 decomposition, their action, whatever it may be, must be slow, and, I should infer, nearly 

 imperceptible. Indeed, I am rather disposed to regard its favorable operation, if indeed 

 it has any, as flowing from a mechanical agency, after the manner of a clay, than as 

 arising from the liberation of its potassa through chemical decomposition. Not that I 

 would call in question the usefulness of the earth taken as a whole, for happily this is 

 too well established. But when I find a decided content of sulphate of lime, with carbon, 

 ate and phosphate of lime in addition thereto, together with distinct traces of organic 

 matter, it appears to me unnecessary to loojc any farther in order to account for the phe- 

 nomena in the case. 



I now proceed to state my method of examination, together with the results obtained. 

 The specimens were kept in a dry room, exposed to air in shallow dishes, for several 



weeks; after which, portions free from crystals of sulphate of lime visible by the naked 

 eye, and large fragments of shells, were heated in a platina -capsule to 300^, Fah., in 

 order to expel hygrometric moisture, and subsequently to low redness, to decompose or- 

 ganic matter. II The organic matter is very inconsiderable, and was in no instances rigidly 

 determined. 



_ Having ascertained by experiment that the iron-pyrites Avas not decomposable by tepid 

 dilute hydrochloric acid, the following method was resorted to for the determination of 



♦ Farmers' Register, vol. ii., p. 131. 

 t Sliepard's Mineralogy, vol. ii., p. 225.- 

 X Idem, ii., p. 225. 

 § Idem, ii., p. 41. 



II This last step was always attended with the extrication of a little sulphur. 



