ng-point of a multitude of important
labours with which the sciences have been enriched during several years.

The chief of these is that of the dark radiating heat which is found
mixed with light.

In studying the phenomena, no longer with the eye, like Newton, but with
a thermometer, Herschel discovered that the solar spectrum is prolonged
on the red side far beyond the visible limits. The thermometer sometimes
rose higher in that dark region, than in the midst of brilliant zones.
The light of the sun then, contains, besides the coloured rays so well
characterized by Newton, some invisible rays, still less refrangible
than the red, and whose warming power is very considerable. A world of
discoveries has arisen from this fundamental fact.

The dark heat emanating from terrestrial objects more or less heated,
became also subjects of Herschel's investigations. His work contained
the germs of a good number of beautiful experiments since erected upon
it in our own day.

By successively placing the same objects in all parts of the solar
spectrum Herschel determined the illuminating powers of the various
prismatic rays. The general result of these experiments may be thus
enunciated:

The illuminating power of the red rays is not very great; that of the
orange rays surpasses it, and is in its turn surpassed by the power of
the yellow rays. The maximum power of illumination is found between the
brightest yellow and the palest green. The yellow and the green possess
this power equally. A like assimilation may be laid down between the
blue and the red. Finally, the power of illumination in the indigo rays,
and above all in the violet, is very weak.

Yet the memoirs of Herschel on Newton's coloured rings, though
containing a multitude of exact experiments, have not much contributed
to advance the theory of those curious phenomena. I have learnt from
good authority, that the great astronomer held the same opinion on this
topic. He said that it was the only occasion on which he had reason to
regret having, according to his constant method, published his labours
immediately, as fast as they were performed.

LAPLACE.

Having been appointed to draw up the report of a committee of the
Chamber of Deputies which was nominated in 1842, for the purpose of
taking into consideration the expediency of a proposal submitted to the
Chamber by the Minister of Public Instruction, relative to the
publication of a new edition of th