of this sort and constitutes the gravest obstacle to the acquisition of well-founded notions.  All that we may hope is that with time the uncertainty of the problem will gradually diminish, demonstrating if not what the geminations are, at least what they cannot be.  We may also confide a little in what Galileo called “the courtesy of nature,” thanks to which a ray of light from an unexpected source will sometimes illuminate an investigation at first believed inaccessible to our speculations, and of which we have a beautiful example in celestial chemistry.  Let us therefore hope and study.

FOOTNOTES: 

[Footnote A:  Pyrois I take to be some terrestrial region, although I have not been able to find any translation of the name.—­Translator.]

[Footnote B:  This observation of the dark color which deep water exhibits when seen from above is found already noted by the first author of antique memory, for in the Iliad (verses 770-771 of Book V) it is described how “the sentinel from the high sentry box extends his glance over the wine-colored sea, [Greek:  oinopa phonton].”  In the version of Monti the adjective indicating the color is lost.]

[Footnote C:  In a footnote the author refers to a drawing of Mars made by himself, September 15, 1892, and says, ...  “At the top of the disk the Mare Erythraeum and the Mare Australe appear divided by a great curved peninsula, shaped like a sickle, producing an unusual appearance in the area called Deucalionis Regio, which was prolonged that year so as to reach the islands of Noachis and Argyre.  This region forms with them a continuous whole, but with faint traces of separation occurring here and there in a length of nearly 6,000 kilometers (4,000 miles).  Its color, much less brilliant than that of the continents, was a mixture of their yellow with the brownish gray of the neighboring seas.”  The interesting feature of this note is the remark that it was an unusual appearance, the region referred to being that in which the central branch of the fork of the Y appeared.  Since no such branch was conspicuously visible this year, it would therefore seem from the above that it was the opposition of 1892 that was peculiar, and not the present one.—­Translator.]

[Footnote D:  This map may be found also in La Planète Mars, by Flammarion, page 44.—­Translator.]