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: 
CONTENTS OF VOL. L. 
NUMBER CXLVUL. 
Art. I.—Photometric Experiments. Parr Szconp.—On the 
amount of light transmitted by plates of polished crown 
glass at a perpendicular incidence; by Oaprn N. Roop, 
II.—The Ethers of Arsenic Acid and of Arsenious Acid; by 
Ole SAN Tg aceisniset cyte aaa pommpeinsna 
III.—On the probable seat of Voleanic Action ; by T. Srzerry 
Hunt, . 
IV.—Notes on some features of the Flora of Kastern Kan- 
sas; by Exrav Haw 
V.Notice of some Minerals from New J ersey; by Prof. 
W. T. Reprer, 
VI.—On the size of Atoms; by Prof, Sir W. THOMSON,. --- 
VIL—Miscellaneous Optical ) Notices; by Woxcorr Gisss, - 
VIIL—On the Occurrence of a Peat bed beneath deposits 
of Drift in Southwestern Ohio, 
IX.—On the Theoretical Temperature of the Sun, under the 
hypothesis of a Gaseous Mass maintaining its Volume 
by its Internal Heat, and depending on the Laws of 
Gases as known to Terrestrial Experiment; by J. Homer 
Lang, 
X.—On the mode of observing the coming Transits of Ve- 
hus; by Simon Nrewcoms, 
pa aes the Geology of Eastern New England; by Dr. T. 
Sterry Hunt, 
XIL—Mineralogical Contributions; by Cartes Upnam 
oe, Ss emer er cone oe nae 
XII —Notive of a new Species of Gavial from the Eocene 
of New Jersey; by Prof. O. C. Marsu, 
XIV.—On Hydrogenium-amalgam; by O. Lorw, --..-.-.-- 
XV.—The eR aan a Division of Annelida ; by Epwarpb 
S. Morse, ..-. 
A New Comet, 
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