DR. W. HUGGINS ON THE PHOTOGRAPHIC SPECTRA OF STARS. 
687 
§ XVI. The Planets. 
Venus .—Several photographs of this planet have been taken, together with a broad 
daylight spectrum. In the most perfect of these photographs, the Fraunhofer lines 
can be distinctly seen from h to S in the ultra-violet, and any differences, even if 
very slight between the planetary spectra and the daylight spectrum, could be at once 
recognised. I cannot, however, discover any additional absorption lines, nor any 
modifications of the solar light. In our early eye observations, Dr. Miller and 
myself failed to detect any change due to the atmosphere of this planet. The photo¬ 
graph shows even no strong general absorption of the blue and violet region. 
Jupiter and Mars .—Similar photographs have been taken of these planets, but they 
fail to show any planetary modification of the solar light in the photographic region. 
In the visible region of the spectra of these planets, Dr. Miller and myself observed 
lines due to the atmospheres of these planets.'" 
§ XVII. The Moon. 
During the last two years a large number of photographs of the light from limited 
areas of the lunar surface have been taken under very different conditions of illumination, 
and also during partial eclipses of the moon. 
Most of these photographs present great differences in the relative general intensity 
of the ultra-violet region, but I have not been able to detect any indications of selective 
absorption. I am inclined to think that the differences of intensity of the more 
refrangible part of the spectrum which I have mentioned are not greater than may be 
accounted for on the ground of differences of intensity of the reflected light as a whole, 
and cannot therefore be taken as an evidence of the existence of a lunar atmosphere. 
The Map. 
M. Cornu’s map of tins region of the spectrum is placed at the top and bottom of 
o 
the map. The portion from G to II is on the same scale, and for this part Angstrom’s 
map of the solar spectrum has been made use of. An attempt has been made to give, 
approximately, the relative intensity and character of the stellar lines. The lines have 
been carefully laid down, but for any purposes requiring great accuracy, use should be 
made of the tables of wave lengths. 
* Phil. Trans., 1864, pp. 421, 423. For a discussion of the observations of other astronomers on the 
visible spectra of the planets, see Vogel’s, 1 Uber die spectra der Planeten.’ 
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