364 M. C. Lea on certain phenomena of Light. 
banks and contain shells of existing species, while a more 
trenchant line of demarkation is nowhere seen than between 
upper part of the Hocene is a hard gray rock, about four 
feet thick, abounding in large green grains, and holding numer- 
ous fossil remains, among which Aturia is most characteristic 
of the geological age of the formation ; below this of unknown 
depth is the loose green-sand with a few Eocene species of 
reptiles, mammals, fishes and plants. 
Arr. XXXV.—On certain Phenomena of Transmitted and 
Diffused Light ; by M. Canny Lza, Philadelphia. 
This experiment, which admits of some very interesting varia- 
be mentioned farther on, is, I believe 
not difft 
