1884. J 
251 
Stellar Photography. 
state of life. The late Sir W. Siemens made some experi- 
ments on the adtion of the eledtric light, which contains a 
very large percentage of chemical light. He found that 
when plants were exposed to its light they grew at a great 
rate. Fruits could thus be forced at any season of the year. 
But he also found that if the light was left bare it quickly, 
by its chemical intensity, killed the plants. To prevent this 
the light was placed in a glass globe, glass being a great 
absorbing medium of the chemical rays of light. 
Various attempts have been made to photograph the stars. 
Prof. Pickering, in America, has photographed the Northern 
Heavens, to make a map and determine the magnitudes. 
The writer of the present paper has endeavoured to go a 
step further, and tried to determine relatively the chemical 
light in the stars by means of photography. Using a lens 
over 2 inches in aperture, various plates were taken of the 
most prominent stars with very interesting results. Alpha 
Lyrae, which is a very white star, left an impression on the 
plate with only five minutes’ exposure. Alpha Cygni, a star 
of the same colour, impressed itself with equal rapidity. 
With long exposures, of one hour and a half, as many as 
120 stars were photographed on a plate of greater size. On 
one plate over forty stars were photographed in the Pleiades, 
a cluster the stars of which seem to possess a large amount 
of chemical light. The red or orange stars, as was to be 
expedted, came out comparatively faint on the plate. In 
the case of a Cete, a star consisting of a second magnitude 
orange star and a mag. blue, a result was found confirming 
Prof. Pickering, viz., that the blue star came out the brighter 
of the two. In some cases, however, where there is little 
or no difference in colour to the eye, the impression on the 
plate in no way corresponds to the star’s magnitude. Hence 
a new line of research is opened up — a research into the 
adtinic light of the stars. Using the ordinary magnitude 
scale as the basis, it is possible to deduce magnitudes from 
the photographic plate and -compare them with the eye 
magnitude. Obviously all the stars photographed will fall 
into one of three classes ; they will be equal in magnitude 
to the star’s magnitude as determined by the eye, or they 
will be above it, or else below it. Hence we have a new 
method of determining accurately the star magnitudes, on 
the one hand, and on the other of cataloguing stars whose 
chemical light is either greater or less than the light that 
affedts the eye. The star magnitudes can be determined 
from the photographic plate with the greatest accuracy, and 
with one great advantage — that the photograph can be taken 
