1852, April 24, 
1857, April 4, 
[11 
Di 
Di 
1860, Jan. 
“ 
EE 
Di 
Di 
ON 
sët E 
€: 98, 
"590, 
May 6, 
[7 8, 
Oct. 3, 
« 7,* 
o 8,* 
& 8, 
D 9,* 
30, 
“80, 
Feb, 7, 
April 6, 
* CN 
THE LIGHT OF 
Moon, 
[11 
[11 
Jupiter, 
Moon, 
Jupiter, 
Moon, 
Jupiter, 
Moon, 
Di 
“ 
THE MOON 
Exposure 20 
Di 
227 
AND OF THE PLANET JUPITER. 
Daguerrotype. 
13 Collodion. 
80 & 
60 8 
45 « 
13 “ 
4 Faint action in < 15. & 
4 or Ar, not well determined. " 
2 or 3 times as long as on 3d. * 
Same as for average of Moon's surface. “ 
33 ? ei 
20? " 
16 z 
13 Di 
7 Di 
A Di 
13 x 
From the above, and from other trials of which no precise record was preserved, I 
conclude that, with the chemical preparations used, the times of exposure for strong 
“ negatives 
at different altitudes, t are as follows: — 
v= 60 
y= 90 
v = 120 
v — 150 
v = 180 
” of the Moon at different phases, after applying a correction for extinction 
Exposure — 30 
* == 20 
E I5 
d =D 
« mh 
It is not easy to decide with certainty respecting these times without experiments 
made especially for the purpose. 
When the object in view is solely the production of 
a good picture, as was the case here, the exposure cannot be continued long enough to 
give a strong negative of the regions towards the dark limb, near the quadratures, 
without injury to the image of the bright limb by over-exposure. 
For an equally intense picture of the planet, the time of exposure is 
ges 175° 
Exposure = 15° 
* On examining the object-glass, Oct. 11th, moisture was found deposited between the lenses, which proba- 
bly affected the experiments on Oct. 7th, 8th, and 9th. 
T Assumed to be the same as for the optical rays. 
