Scientific American Supplement, No. 483, April 4, 1885Various
Science
Scientific American Supplement, No. 483, April 4, 1885
Various
Science -- Periodicals
With the alteration of declination of the sun, the light entering the
camera is reflected from different portions of the sphere, and an
alteration of the position of the focus results. This may be corrected in
three ways; by moving (1) the paper, (2) the lens, or (3) the sphere. In
the present apparatus the first method has been adopted, and now the
camera is about twice as long as it was in June. As a consequence, the
circular image is enlarged, and the light therefore weakened, and that at
a time of year when it can least be spared. If the focus is altered by
moving the lens, the winter circle is small and the summer circle is much
larger. This would perhaps be too much to the advantage of the winter
sun. If, however, the lens and paper are maintained at a constant
distance, and the sphere alone moved, the circles are more nearly of the
same diameter throughout the year, the winter one still remaining the
smallest. This seems, therefore, to be the most advantageous arrangement,
and the one that will be adopted in future. It may be possible also to
find positions for the sphere, lens, and paper such that the intensity of
the image is a true measure of the intensity of the sun's light; at
present, however, this has not been done, the want of sunlight and the
press of official work having prevented the carrying out of the necessary
experiments. A more sensitive paper might also be used with advantage,
and in observatories where photographic processes are carried on daily
there would be no difficulty on this score, but my principal object was
to devise some economical instrument requiring only easy manipulation, so
that at a considerable number of places the instruments might be set up,
giving a more useful average of the duration of sunshine than can be
obtained from only a few stations. The instrument also gives a record
when the sun is shining through light clouds; in this case the image is
somewhat blurred and naturally weakened, and it may be difficult or
impossible to employ any scale for measuring the intensity under such
conditions, but it must be remembered that, even when the sun is shining
in this imperfect manner, it is really doing work on the vegetation of
the earth, and deserves to be recorded.
It may be well to say that the instrument is in no way protected. Some
friends, whose opinion I highly value, urged me to patent it; but as I
strongly hold the view that the work of all students of science should be
given freely to the world, the apparatus was described at the Physical
Society a few hours after the advice was given, lest the greed of filthy
lucre should, on further deliberation, cause me to act contrary to my
principles.--_Herbert McLeod, Nature_.
* * * * *
SKELETON OF A BEAR FOUND IN A CAVE IN STYRIA, AUSTRIA.
Public-domain text, read in full here on John Shaqi.
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