248 PROCEEDINGS OF THE ACADEMY OP [1880. 



26. Germantown, Pa. Large silvery plates. 



27. Dixon's Quarry, Del. Pale green. 



28. Connecticut. Green scales. (A. !N^. S.) 



29. Georgetown, Col. 



30. Upland, Del. Co., Pa. Pale green. (.J. M. 



Cardeza.) 



31. Germantown, Pa. Pale green. 



32. Chester Co., Pa. (A. N. S.) 



33. Westchester Co., N. Y. 



34. Fabyans, White Mountains, N. H. 



35. Glacier of the Aar, Switz. (A. N. S.) 



36. Trumbull, Conn. Margarodite. 



37. Paris, Me. Rose-color. (A. ]S^. S.) 

 Where not otherwise indicated, the above muscovites are of a 



clear j^ellowish-brown tint. 



Lepidolite. 



1. Altenberg, Saxony. With Pycnite ; sometimes 



distorted. (A. N. S.) 31°. 



2. Zinnwald, Bohemia. Often very irregular. On 



different parts of the same piece the angle 



varies from 34°30' to 51°30'. (A. N. S.) 49°30' 



3. Paris, Me. Much distorted ; several axes. (A. 



N. S.) 60°±:. 



4. Middletown, Conn. 66°. 



Talc. 



1. Lafayette, above Manayunk, Pa. Exfoliating : 



fan-shaped cr3^stals : images much distorted. 12°40'. 



2. Lafayette, Pa. Clear. 15°. 



3. Lafayette, Pa. Foliated talc ; distorted images. 15°. 



4. Harford Co., Md. White. 15°. 



5. Shetland Is. Clear pale green, sometimes nearly 



uniaxial. • 17°. 



Pyrophyllite. 

 Westana, Sweden. 106°51'. 



Serpentine. 



Chrysotile from Chester Co., Pa., shows strong double refraction 

 when the fibres make an angle of 45° with the plane of polariza- 



