To descend, for a moment, to details. Sir David Brewster will not allow himself to be driven to elect between the icy or watery constituency of Jupiter. He declares direct experiment to have proved that it is neither; that if Jupiter were a sphere of water, the light reflected from his surface, when in his quadratures, must contain, as it does _not_, a large portion of polarised light; and if his crust consist of mountains, precipices, and rocks of ice, some of whose faces must occasionally reflect the incident light at nearly the polarising angle, the polarisation of their light would be distinctly indicated. The Essayist, in his _Dialogue_, “doubts whether the remark is applicable; for Jupiter’s watery or icy mass must be clothed in a thick stratum of air, and aqueous vapour, and clouds. But even were the planet free from clouds, the parts of the planet’s surface from which polarised light would be reflected, would be only as points compared with the whole surface; and the common light reflected from the whole surface would quite overwhelm and obliterate the polarised light.”—_Dial._ p. 64. We cite this as a sample of the ingenuity of both disputants, in a point of scientific contact. Whether Sir David’s conjectural polarised light be or be not thus obliterated, in our view the item in dispute is quite lost in the general question, and the great principles on which its solution depends. If driven to elect between ice and water, asks Sir David playfully, “may we not, upon good grounds, prefer the probable _ice_ to the possible water, and accommodate the inhabitants of Jupiter with very comfortable quarters, in huts of snow and houses of crystal, warmed by subterranean heat, and lighted with the hydrogen of its waters, and its cinders not wholly deprived of their bitumen?”—Pp. 236, 237. The answer of his opponent would be obvious. Footnote 87: Brewster, p. 61. Footnote 88: Ibid., p. 62. Footnote 89: Ibid., pp. 65, 66. Footnote 90: Ibid., pp. 68, 69. Footnote 91: _Dial._, p. 6. Footnote 92: Ibid., p. 23. Footnote 93: _Dial._, p. 76. Footnote 94: _Museum_, &c., vol. i. p. 35. Footnote 95: _Dial._, p. 23. Footnote 96: Lord Byron—Hebrew Melodies. “The philosopher will scan,” says Sir David, at the close of his eloquent Treatise, “with a new sense, the lofty spheres in which he is to study.”—P. 259. Footnote 97: Pp. 164, 165. Footnote 98: Isaiah, xlv. 9. Footnote 99: Isaiah, lv. 8, 9. Footnote 100: _Essay_, p. 244. Footnote 101: Pp. vii.–viii. Footnote 102: _Essay_, pp. 243, 244. Footnote 103: See them specified, p. 251. Footnote 104: _Cosmos_, iii. 373. Footnote 105: Ch. viii., _passim_. Footnote 106: _Dial._, pp. 20–23. Footnote 107: _More Worlds than One_, Ch. vi., _passim_. Footnote 108: _More Worlds than One_, Ch. viii., _passim_. Footnote 109: Ibid., p. 164. Footnote 110: Ibid., p. 119.