atellite present to Venus must be so varied and wonderful
that one might well wish to visit that planet merely for the sake of
beholding them.

Thus far we have found so much of brilliant promise in the earth's twin
sister that I almost hesitate to approach another phase of the subject
which may tend to weaken the faith of some readers in the habitability
of Venus. It may have been observed that heretofore nothing has been
said as to the planet's rotation period, but, without specifically
mentioning it, I have tacitly assumed the correctness of the generally
accepted period of about twenty-four hours, determined by De Vico and
other observers. This period, closely accordant with the earth's, is, as
far as it goes, another argument for the habitability of Venus.

But now it must be stated that no less eminent an authority than
Schiaparelli holds that Venus, as well as Mercury, makes but a single
turn on its axis in the course of a revolution about the sun, and,
consequently, is a two-faced world, one side staring eternally at the
sun and the other side wearing the black mask of endless night.

Schiaparelli made this announcement concerning Venus but a few weeks
after publishing his discovery of Mercury's peculiar rotation. He
himself appears to be equally confident in both cases of the
correctness of his conclusions and the certainty of his observation. As
with Mercury, several other observers have corroborated him, and
particularly Percival Lowell in this country. Mr. Lowell, indeed, seems
unwilling to admit that any doubt can be entertained. Nevertheless, very
grave doubt is entertained, and that by many, and probably by the
majority, of the leading professional astronomers and observers. In
fact, some observers of great ability, equipped with powerful
instruments, have directly contradicted the results of Schiaparelli and
his supporters.

The reader may ask: "Why so readily accept Schiaparelli's conclusions
with regard to Mercury while rejecting them in the case of Venus?"

The reply is twofold. In the first place the markings on Venus, although
Mr. Lowell sketched them with perfect confidence in 1896, are, by the
almost unanimous testimony of those who have searched for them with
telescopes, both large and small, extremely difficult to see,
indistinct in outline, and perhaps evanescent in character. The sketches
of no two observers agree, and often they are remarkably unlike. The
fact has already been mentioned