ch represents to us the
massive bulk of Uranus, by Young, Schiaparelli,[1132] Safarik, H. C.
Wilson[1133] and Perrotin, prove it to be quite distinctly _bulged_. The
compression at once caught Barnard's trained eye in 1894,[1134] when he
undertook at Lick a micrometrical investigation of the system; and he
was surprised to perceive that the major axis of the elliptical surface
made an angle of about 28 deg. with the line of travel pursued by the
satellites. Nothing more can be learned on this curious subject for some
years, since the pole of the planet is just now turned nearly towards
the earth; but Barnard's conclusion is unlikely to be seriously
modified. He fixed the mean diameter of Uranus at 34,900 miles. But this
estimate was materially reduced through Dr. See's elimination of
irradiative effects by means of daylight measures, executed at
Washington in 1901.[1135]

The visual spectrum of this planet was first examined by Father Secchi
in 1869, and later, with more advantages for accuracy, by Huggins,
Vogel,[1136] and Keeler.[1137] It is a very remarkable one. In lieu of
the reflected Fraunhofer lines, imperceptible perhaps through feebleness
of light, six broad bands of original absorption appear, one
corresponding to the blue-green ray of hydrogen (F), another to the
"red-star line" of Jupiter and Saturn, the rest as yet unidentified. The
hydrogen band seems much too strong and diffuse to be the mere echo of a
solar line, and might accordingly be held to imply the presence of free
hydrogen in the Uranian atmosphere. This, however, would be difficult of
reconcilement with Keeler's identification of an absorption-group in the
yellow with a telluric waterband.

Notwithstanding its high albedo--0.62, according to Zoellner--proof is
wanting that any of the light of Uranus is inherent. Mr. Albert Taylor
announced, indeed, in 1889, his detection, with Common's giant
reflector, of bright flutings in its spectrum;[1138] but Professor
Keeler's examination proved them to be merely contrast effects.[1139]
Sir William and Lady Huggins, moreover, obtained about the same time a
photograph purely solar in character. The spectrum it represented was
crossed by numerous Fraunhofer lines, and by no others. It was, then,
presumably composed entirely of reflected light.

* * * * *

Judging from the indications of an almost evanescent spectrum, Neptune,
as regards physical condition, is the twin of U