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THE SOUECE OF HEAT IN THE SUN. 
BY EOBEET HUNT,, F.E.S. 
KX 
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I NDIJCTIYE science^ moving hand in hand with deductive 
philosophy, is rapidly adding to the stores of human 
knowledge. By experiment and by observation, facts are 
rapidly being accumulated, and the powers of the mind are 
ever active in interpreting their significations. No department 
of science has been more productive of new and great truths, 
tending to enlarge our mental vision, than that division of 
physics which has taken the Sun and its radiations for the 
objects of investigation. It may be that some of the pheno- 
mena observed will eventually receive a different solution from 
that which they now receive, and it is probable that some of 
the hypotheses which have gained the approval of the most 
thinking minds, will give place to others ; but certain it is 
that we are placed, with improved perceptions, upon an 
elevated spot, and our horizon is vastly enlarged. The mind 
of man, over-reaching the immensity of space between this 
little planet and the giant Sun, to which it is chained, lands 
I upon the solar surface and investigates its phenomena. It is 
by no system of vague guesses that we proceed upon this 
inquiry : every step in advance is secured upon a well-deter- 
I mined fact ; and each hypothesis by the fight of which we are 
guided, is the result of the profound study of observed pheno- 
j mena. In this brief essay, we shall endeavour to give all the 
evidence which is of importance, as leading to the conclusions 
to which modern philosophy has arrived, respecting the con- 
stant renewal of the solar energies. 
Our inquiry into the origin and support of solar heat in- 
volves a consideration of the sources also of the luminous and 
the chemical {actinic) powers — since these are associated with 
calorific force in the sunbeam — and are, without doubt, deve- 
loped by the operation of the same causes. Nor must it be 
forgotten that those electrical manifestations, which are familiar 
1 to us in the phenomena of terrestrial magnetism, are evidently 
connected with solar perturbations. 
By the operation of some peculiar exciting powers, the solar 
energies are developed and radiated from that great centre in 
VOL. IV. NO. XIV. L 
