38 
POPULAR SCIENCE REVIEW. 
CONDITION OF THE LARGER PLANETS. 
By RICHARD A. PROCTOR, P.R.A.S. 
M VOGEL’S recent researches’into the spectra of the planets 
• are regarded by him as affording evidence unfavourable 
to the opinion that the planets Jupiter and Saturn are still so 
intensely hot as to shine in some degree with inherent light. 
Although it is not at all necessary for the general theory which 
I have advocated respecting the condition of the larger planets 
that any portion of their lustre should be regarded as inherent, 
yet as Vogel’s conclusion does bear to some degree on one of 
the arguments which have been urged in favour of this theory, 
the opportunity seems convenient for summing up these argu- 
ments and discussing briefly the considerations on which M. 
Vogel bases his objection. 
I would remark at the outset that I do not by any means 
share the opinion of some who, in dealing with this question, 
and other questions of a like nature, have said that it matters 
very little what theory is adopted so that it is a convenient 
working hypothesis, a string, so to speak, on which to thread 
the observations. It will be found that this method of viewing 
matters is never expressed except by persons who have fallen into 
the habit of accumulating observations without reasoning upon 
them, — in fact, without utilising them. Observation is with them 
not a means but an end. It seems to me, or rather I may speak 
more confidently and say that the whole history of science proves, 
that the real value of observation and experiment lies not in 
themselves, but in what may be deduced from them. They are 
the raw material whence scientific knowledge is to be manu- 
factured. It is not the object of a theory to afford a convenient 
means of classifying observations and also to suggest occasion 
for making them, but to educe their real significance ; and the 
sole reasonable object of observations is to suggest the true 
theory and to afford the means of testing and rejecting false 
ones. To assert that it matters little what theory is suggested 
so long as it affords a convenient means of classifying observa- 
tions, is as absurd in reality as it would be to assert that it 
