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POPULAR SCIENCE REVIEW. 
advance of our knowledge lias been rapid. We know of 
luminous rays which were never seen by that philosopher. Of 
the chemical action of light he was ignorant. The beautiful 
phenomena of the Polarization of Light were unknown to him, 
and of the existence of numerous dark lines crossing even the 
most brilhant divisions of the Newtonian spectrum — and which 
promise to advance our knowledge by the discovery of many 
sublime truths, — he had not the most remote idea. Yet, not- 
withstanding this want of the knowledge with which we are 
familiar, Newton possessing, in a remarkable degree, that power 
of thinking out a truth, which showed itself so strongly in the 
philosophers of Athens, proposed an hypothesis, which has been 
set aside and almost forgotten, but to which we are now return- 
ing, to adopt it as the most truthful theory of the physical 
condition of the Sun. 
With the following quotation from Newton’s “ Optics,” let us 
fairly introduce the inquiry, which, with every advance, appears 
to confirm his views : — 
“May not great, dense, and fixed bodies, when heated 
beyond a certain degree, emit fight so copiously, — as, by the 
emission and reaction of then- fight, and the reflections and 
refractions of them rays within their pores — to grow still hotter, 
till it comes to a certain period of heat, such as is that of the 
Sun ? 
“ And, are not the Sun and fixed stars great earths, 
vehemently hot, whose heat is conserved by the greatness of 
the bodies, and the mutual action and reaction between them 
and the fight which they emit?” — ( Newton’s Optics .) 
Since Newton’s days, this hypothesis for a considerable 
g niod was discarded, and more especially so, since Sir William 
erschel gave to the world his investigations on the solar 
spots. The prevailing idea has been that the Sun is a dark 
mass ; that floating above it there exists a stratum of opaque 
clouds ; and that surrounding — enveloping — those is the 
Photosphere, or sphere of fight, whence we derive the 
luminous powers on which vision and colour are dependent. 
Arago and Biot determined, by a series of beautifully devised 
experiments, dependent on the phenomena of the polarization 
of fight, and by careful observations, that the luminous 
principle, originating in the photosphere, is produced by a 
gaseous or vaporiform medium in a state of intense combustion. 
This discovery did not, however, interfere with the idea that 
the mass of the Sun was dark and cold. It is only within a 
very recent period that inquiries in a new direction have 
taught us to doubt the correctness of the views originating 
with the elder Herschel, and have led us back to the specula- 
tions of Newton. 
