INORGANIC COMrOSITION OF SOME AMERICAN SOILS. 23 



birefringence of pyrophyllite. They are not to be confused with the 

 fibrous variety of epidote which has a much higher refractive index 

 and results from the alteration of plagioclase feldspars; chlorite and 

 magnetite are also present. 



(22) YORK SILT LOAM, SUBSOIL. 



No. If. sand. — Minerals other than quartz, 10 per cent. No potash 

 feldspars. Muscovite, 2 per cent. Magnetite, biotite, and tour- 

 maline present. 



No. 5 sand. — Minerals other than quartz, 12.7 per cent. No potash 

 feldspars. Muscovite, 1 per cent. Pyrophyllite present in large 

 quantities. Magnetite, chlorite, tourmaline, and epidote also present. 



Silt. — Minerals other than quartz, 85 per cent. Characterized by 

 a high muscovite and pyrophyllite content. Rutile present. 



(23) LOUISA LOAM, SOIL. 



No. 5 sand. — Minerals other than quartz, 7.7 per cent. Magnetite, 

 zircon, chlorite, muscovite, and apatite inclosed in quartz are present. 



Silt. — Minerals other than quartz, 51 per cent. Potash feldspars, 3 

 per cent. Muscovite, 2.3 per cent. Magnetite, biotite, epidote, and 

 chlorite predominate; tourmaline, zircon, and rutile are also present. 



(24) LOUISA LOAM, SUBSOIL. 



No. 5 sand. — Minerals other than quartz, 10 per cent. Magnetite, 

 zircon, hematite, and apatite inclusions in quartz are present. 



Silt. — Minerals other than quartz, 60 per cent. Potash feldspars 

 (orthoclase) , 2.5 per cent. Muscovite, 1.7 per cent. Biotite, chlorite, 

 orthoclase, and muscovite predominate; epidote, zircon, magnetite 

 diallage, and rutile are also present. 



(25) PENN SILT LOAM, SOIL. 



No. 4 sand. — Minerals other than quartz, 10 per cent. Potash 

 feldspars (orthoclase), 1 per cent. Muscovite, 6 per cent. Labra- 

 dorite, zircon, apatite inclosed in quartz, hornblende, rutile, mag- 

 netite, and hematite are also present. 



No. 5 sand. — Minerals other than quartz, 15 per cent. Potash feld- 

 spars (orthoclase), 6 per cent. Muscovite, 4 per cent. Magnetite, 

 hematite, labradorite, tourmaline, hornblende, andalusite, zircon, 

 and albite-oligoclase are also present. 



Silt. — Minerals other than quartz, 18 per cent. Potash feldspars 

 (orthoclase), 5 per cent. Muscovite, 9 per cent. Tourmaline, bio- 

 tite, epidote, hornblende, albite, apatite, and augite are also present. 



