J. P. Cooke on Aqueous Lines of the Solar Spectrum. 179 
east side of my laboratory was 70° F., while the wet bulb ther- 
mometer indicated 66°, showing an amount of moisture in the 
atmosphere equal to 6°57 grains per cubic foot. At the same 
time the atmosphere was beautifully clear and the sun shone with 
ita full splendor. I have never seen the aqueous lines of the 
> sede more strongly defined than they were on this day, and 
the total number of lines visible in the yellow portion of the © 
spectrum was at least ten times as great as are ordinarily seen. 
A 2. 
January 5, 1866. December 25, 1865. 
Temperature 10° F. Temperature 46° F 
Dew Point 19°5 F. Dew Point 33°4 F. 
‘ D, * = D, D, \ @ B D, 
Weight of Vapor in one , Weight of Vapor in one } 9. . 
Cubic Foot of Air, host Cyne Cubie Foot of Air, t aaa; 
3. 4. 
December 26, 1865. November 17, 1865. 
Temperature 55° F. Temperature 70° F. 
Dew Point 46° F. Dew Point 64° F. 
+. , 
D,o2¢¢ a8 Dz es bese mite « 
Weight of Vapor in one : Weight of Vapor in one Lest i 
Cubie Foot of Air, Late om Cubic Foot of Air, sae 
The appearance of the D line on that day is shows: in fig. 4 
Between the two familiar broad lin » A there..were 
