306 
POPULAR SCIENCE REVIEW. 
The “ mental purity” which Sir John Herschel advocated u as that quality 
which alone can fit us for a full and ready perception as well of moral 
beauty as of physical adaptation,” is after all but another word for mental 
strength. The effort to loosen the hold on all which might interfere with 
the ready admission of truth is, as Herschel justly said, “the 1 euphrasy and 
rue’ with which we must 1 purge our sight’ before we can receive and 
contemplate as they are the lineaments of truth and nature but it is 
chiefly to be valued as indicative of strength of mind ; while the seeming 
firmness of grasp with which some men retain their hold, with vice-like 
tenacity, upon favourite theories, is as far from showing real strength as the 
clutch of a convulsed person. It is well, then, to note how ©ur greatest 
astronomer — like Newton and Sir William Herschel, the greatest astro- 
nomers of other days — was submissive to truth, patient to hear the reason- 
ing of others, and ready to yield his own opinions when sufficient arguments 
were urged against them.* 
The Spectrum of Uranus. — Dr. Huggins has already begun to do good 
work with the fine telescope placed in his handb by the Royal Society. 
With the 8-inch equatorial he employed before, he found the light of 
Uranus too faint to be satisfactorily examined with the spectroscope. But 
with the 15 inches of aperture of the refractor by Grubb, he has succeeded 
in studying the planet to some purpose. His results are not in accordance 
with those obtained by Fr. Secchi in 1869. Fr. Secchi then remarked of 
the spectrum of Uranus : “Le jaune y fait completement defaut. Dans le 
vert et dans le bleu il y a deux raies tres-larges et tres-noires.” The band 
in the blue he represented as less refrangible than F, and the one in the 
green as near E. On the contrary, Dr. Huggins describes the spectrum of 
Uranus as “ continuous, without any part being wanting, as far as the feeble- 
ness of its light permits it to be traced, which is from C to about G.” The 
most marked absorption lines in the spectrum of Uranus are six. One of 
these (the most refrangible) is at or very near the position of F in the solar 
spectrum. The light from a tube containing rarefied hydrogen, rendered 
luminous by the induction spark, was compared directly with that of 
Uranus, and “ the band in the planet’s spectrum appeared to be coincident 
with the bright line of hydrogen.” Two of the other bands “ appeared to 
be very nearly coincident with bright lines of the spectrum of air, but the 
faintness of the planet’s spectrum did not admit of certainty on the point.” 
“ I suspected,” adds Dr. Huggins, “ that the planetary lines are in a small 
degree less refrangible. There is no strong line in the spectrum of Uranus 
in the position of the strongest of the lines of air, namely, the double line 
of nitrogen. As carbonic acid gas might be considered, without much im- 
probability, to be a constituent of the atmosphere of Uranus, I took mea- 
* We saw, with pain, that in the most elaborate obituary notice of 
Herschel which appeared in the daily press — the biography in the “ Daily 
News ” — the most beautiful qualities of Herschel’s disposition, those which 
specially marked the philosophic nature of his mind, were (most perversely) 
ascribed to vanity — a quality, of all others, most alien to his disposition. 
From internal evidence, we are inclined to believe that this notice, obviously 
written by one who was not a very young man in 1830, came from the pen 
of a certain eminent mathematician, who did not live to see it in print. 
