386 TRANSACTIONS OF SECTION A. 
3. The Lowell Observatory Photographs of Jupiter. 
By Professor Perctvan Low. 
The new system of planetary photography devised and carried out at 
the Lowell Observatory has secured the detailed images of Jupiter here 
presented. Its difficulty as compared with celestial photography in general 
will be realised on considering that in the finest star photographs the 
whole disc of a planet would be a mere point. 
The present results have been got chiefly through the ability of one of 
the staff, Mr. C. O. Lampland, though other members have contributed. 
The undertaking necessitated the utmost definition at every step of the 
process. Among the factors to this end were :— 
1. Selection of the observatory site for steady air. 
2 The remarkable unification of focus of all parts of the glass, the 
24-inch Clark refractor, due to Mr. Lundin. 
3. The securing of a particular colour-screen. 
4. Particular isochromatic plates. 
5. Suitable development. 
6. Guiding by hand. 
7. Adjustment of size of image and exposure time; for Jupiter this 
time was 34-4 seconds. 
Results.—The images disclose a surprising delicacy of detail. Specially 
noteworthy are the faint wisps that crisscross like lacings the several 
belts, particularly the bright equatorial one. Some of these can be seen 
in the drawings of Sir William Huggins, fifty years ago, and their 
complete character was detected by Mr. Scriven Bolton. The small white 
spots which are so peculiar a feature of the disc also come out in the 
images. Transits of the satellites and of their shadows are stamped there, 
sometimes more than one upon a single plate. 
The great number of images taken consecutively on each plate serves 
to part defects in the film or specks on the colour-screen from details on the 
planet. 
Deductions.—1. Measurement of the images shows that, after allowance 
is made for the planet’s axial tilt, the bright equatorial belt lies exactly 
upon the planet’s equator. Thus the clouds which clearly compose it are 
Jove-raised, not sun-raised, ones. 
2. Measurement of the dark belts show that they occupy approximately 
the position of the spot zones on the sun. 
3. The photographs show that the edge of the disc is less luminous than 
the centre, as is also known visually. The same is true of the sun. 
4. The dark belts are a cherry-red. This hue is also vouched for by their 
spectrum, which, taken by another member of the staff, Dr. V. M. Slipher, 
side by side with that of the bright belt, discloses a greater general 
absorption in the blue-green. 
5. Spectrograms by the same show the special Jovian absorption bands 
J, J, more intense, for equal general illumination, in the bright equatorial 
. belt. This does not seem true of Jy. 
6. Miiller’s, the latest determination of Jupiter’s albedo, is 75 per cent. ; 
that of cloud, 72 per cent. This raises a presumption that Jupiter shines 
partly by inherent light. The margin, however, is too small to permit of 
certain deductions—at present. 
7. The belts and wisps are best explained as gaps in the clouds formed 
by condensing of uprising vapours from Jupiter’s heated interior and 
strung out by his rotation. The planet is still a semi-sun. 
4. Harly Drawings of Jupiler. By Sir Wittiam Huaatns, F.R.S.- 
