ON THE LIGHT OF THE MOON AND OF THE PLANET JUPITER. 269 
Jupiter near the meridian, viewed with colored screens, A, D, and C, of different 
densities, but same tint, bluish. E, dense, full red. F, yellow, with tinge of green, 
dense. G, dense blue. K, yellowish red or orange, thin. L, indigo, thin. 
Jupiter, near meridian, seen plainly with A; just discerned with entire certainty 
through A + K and d+ L. Easily with F and G, though they would not bear 
much increase of density. Æ comes nearest to cutting off the whole light, but it is 
still plainly seen, and the red tinge is evident, which would not be the case if the 
light were of the last degree of faintness. The centre of the planet was placed, as 
usual, at the centre of the focus aperture, and the telescope kept in motion by the 
driving clock. The word * Astronomy" on the title-page of Herschel's * Outlines " 
could be read by the light of Sirius near the focus. 
1860, March 19th. 7" 9", Sid. time. Not perfectly clear. Same adjustment as 
on previous nights. Re-examined light of Jupiter with screen A+ K. Seen dis- 
tinctly, though not without difficulty. With E, a decided red tint is distinguished. 
Observations repeated at 9" 30", Sid. time. 
1860, March 23d. 9", m.s.t. Perfectly clear. Adjustments as usual. Jupiter ex- 
amined with screens A + K and E for comparison with experiments elsewhere 
narrated. 
1860, March 24th. 7" 15” to 7" 40", Sid time. Moon two days old, near Venus. 
Aperture 14.94. 
Moon seen with difficulty, though certainly with E, but not with A + K, taking 
the average of the brightest fifth part of the illuminated surface. 
Reduced the aperture to 2".5, and set upon Venus, at 7” 40”, Sid. time. The planet 
was not visible at all with E. Perhaps discerned with A + K. Two hours later, 
Jupiter, with full aperture, showed a strong red with E. 
The eye-piece having been removed, the light of Jupiter transmitted by the object- 
glass was compared with the lamp S, diaphragm Z, by means of the photometer as 
described on p. 247. 
NK | E ix 
941” Sid. time. Contre of bulb wé focus, D -02 To lamp, 22 1.0 
SS 4 19 4 ^ 74$ 19 
WA Uk 4 20 « 99 48 
E x 4 47 “2 48 
à T. 4 47 « 98 10 
a 4117 “26110 
10 9 " d 
VOL. VIII. 95 
