still. A fairly
concordant result was published in 1895 by Mr. B. M. Roszel.[1033] He
found that the lunar globe probably contains forty times, the
terrestrial globe 3,240 times the quantity of matter parcelled out among
the first 311 minor planets. The actual size of a few of them may now be
said to be known. Professor Pickering, from determinations of
light-intensity, assigned to Vesta a diameter of 319 miles, to Pallas
167, to Juno 94, down to twelve and fourteen for the smaller members of
the group.[1034] An albedo equal to that of Mars was assumed as the
basis of the calculation. Moreover, Professor G. Mueller[1035] of Potsdam
examined photometrically the phases of seven among them, of which
four--namely, Vesta, Iris, Massalia, and Amphitrite--were found to
conform precisely to the behaviour of Mars as regards light-change from
position, while Ceres, Pallas, and Irene varied after the manner of the
moon and Mercury. The first group were hence inferred to resemble Mars
in physical constitution, nature of atmosphere, and reflective capacity;
the second to be moon-like bodies.

Finally, Professor Barnard, directly measuring with the Yerkes refractor
the minute discs presented by the original quartette, obtained the
following authentic data concerning them:[1036] Diameter of Ceres, 477
miles, albedo = 0.18; diameter of Pallas, 304 miles, albedo = 0.23;
diameter of Vesta, 239 miles, albedo = 0.74; diameter of Juno, 120
miles, albedo = 0.45. Thus, the rank of premier asteroid proves to
belong to Ceres, and to have been erroneously assigned to Vesta in
consequence of its deceptive brilliancy. What kind of surface this
indicates, it is hard to say. The dazzling whiteness of snow can hardly
be attributed to bare rock; yet the dynamical theory of gases--as Dr.
Johnstone Stoney pointed out in 1867[1037]--prohibits the supposition
that bodies of insignificant gravitative power can possess aerial
envelopes. Even our moon, it is calculated, could not permanently hold
back the particles of oxygen, nitrogen, or water-gas from escaping into
infinite space; still less, a globe one thousand times smaller. Vogel's
suspicion of an air-line in the spectrum of Vesta[1038] has,
accordingly, not been confirmed.

* * * * *

Crossing the zone of asteroids on our journey outward from the sun, we
meet with a group of bodies widely different from the "inferior" or
terrestrial planets. Their gigantic size, low