i 882.] 
Analyses of Books . 
359 
tion that Uranus is considerably more dense than Saturn, and 
that this is scarcely compatible with the hypothesis ; spedtral 
analysis, however, now forcibly pleads, by its results, for such a 
genesis of the planetary system, and it will be therefore admitted 
at present on the whole and in a general way. Yet the Gaussian 
objection is precisely, for the case in question, of great import- 
ance. For, even in meteorology, the physicist finds it an almost 
entirely unsolvable task to determine by calculation the density 
of the strata of the terrestrial atmosphere, with its height of only 
about 16 geographical miles, under the influence of the changes 
of temperature and the consequent motions. This difficulty 
must be increased to an enormous degree in the case of a gas- 
sphere some thousands of millions of miles in diameter cooling 
down from glow heat. In spite of all this and that, it must be 
admitted that the inquiry has been carried through with perspi- 
cacity and ingenuity. 
“ Even an antagonist of metaphysical reasoning and partisan 
of the indudtive method may befriend himself with it on account 
of its euristic value. One here thinks quite spontaneously of the 
so-called Borde-Titius series, which became the occasion to look 
fora planet between Mars and Jupiter. Notwithstanding the 
series cannot be proved, and the result has been another and an 
unexpected one, it may yet not be denied that it has been useful 
to science. But one may also quote an example, how meta- 
physics may mislead on this ground. A short time after Hegel 
had proved in his inaugural address that there could not exist 
any more planets than were known at the time, a new planet 
was discovered, we might think as a warning for all meta- 
physicians and all times. 
“ It is not at all rare that the author of a book is proudest of 
what an unprepossessed criticism cannot approve. This applies 
{or seems to me to apply) to that part of the book in question, 
which tries to prove that the surface of the earth, also the distri- 
bution of water and land, must be exactly so constituted as it is 
known to be. The critic, however, can here only judge that the 
d priori proof contains more than one dark passage, and that 
there also exists no proposition whatever for such a demonstra- 
tion. Its discovery would furnish the subject for a prize theme. 
Yet a directly denying criticism I would not like to exercise , 
because I am not sufficiently at home on this ground, which the 
author appears to be, at least, as far as regards the material. 
■ — Goettingen, February n, 1882 ” 
Appreciating the advantage that an eminent savant has ex 
pressed an opinion on my work, aware that theories now famous 
have fared much worse, and thankfully acknowledging the 
regardful, antithetical, and cautious character of Prof. Klinker- 
fues’s criticism, I point out in the interest of my views some 
erroneous statements and superficial readings. 
It was the pamphlet which engaged the attention of the criti 
