178 J. P. Cooke on Aqueous Lines of the Solar Spectrum. 
of the southern Kentucky wells commence in the Cincinnati 
group of argillaceous limestones and penetrate the underlying 
black shale. 
It seems to have become established from recent researches 
that the petroleum of the northwest not only accumulates in 
several different formations but also originates from materials 
stored up in rocks of different geological ages from the Utica 
slate to the Coal conglomerate, and perhaps the Coal-measures. 
University of Michigan, Jan. 3, 1866. 
Art. XXIV.—On the Aqueous Lines of the Solar Spectrum ;* by 
JosiaH P. CookE, JR. 
A CAREFUL examination of the solar spectrum continued 
during several months with the spectroscope described in a re- 
cent article® in this Journal has led me to the conclusion that 4 
arge number of the more faint dark lines of the solar 
possible to eliminate the effects which might be caused by the 
variations in the condition of the instrument itself; and, 2 
these were known to be very great, it was possible that they 
might account for all the variations observed. With the 1m 
proved instrument, however, just referred to, absolute constancy 
of action is obtained, and all merely instrumental variations 
avoided. 
A peculiar condition of the atmosphere gave the first clue as t0 
the cause of the changes under consideration. The weather °F 
the 17th of November, 1865, at Cambridge, Massachusetts, wa5 
very unusual, even for that peculiar season known in New Eng 
land as the Indian Summer. At noon the temperature on the 
Communicated to the American Academy of Arts and Sciences, Jan. 9, 1866. 
2 Vol. xl, Nov., 1865, 
