ry. The
"canals" of Mars are an actually existent and permanent phenomenon. An
examination of the drawings in his possession showed M. Terby that they
had been seen, though not distinctively recognised, by Dawes, Secchi,
and Holden; several were independently traced out by Burton at the
opposition of 1879; all were recovered by Schiaparelli himself in 1879
and 1881-82; and their indefinite multiplication resulted from Lovell's
observations in 1894 and 1896.

When the planet culminated at midnight, and was therefore in opposition,
December 26, 1881, its distance was greater, and its apparent diameter
less than in 1877, in the proportion of sixteen to twenty-five. Its
atmosphere was, however, more transparent, and ours of less impediment
to northern observers, the object of scrutiny standing considerably
higher in northern skies. Never before, at any rate, had the true aspect
of Mars come out so clearly as at Milan, with the 8-3/4-inch Merz
refractor of the observatory, between December, 1881, and February,
1882. The canals were all again there, but this time they were--in as
many as twenty cases--_seen in duplicate_. That is to say, a twin-canal
ran parallel to the original one at an interval of 200 to 400
miles.[994]

We are here brought face to face with an apparently insoluble enigma.
Schiaparelli regards the "germination" of his canals as a periodical
phenomenon depending on the Martian seasons. It is, assuredly, not an
illusory one, since it was plainly apparent, during the opposition of
1886, to MM. Perrotin and Thollon at Nice,[995] and to the former, using
the new 30-inch refractor of that observatory, in 1888; Mr. A. Stanley
Williams, with the help of only a 6-1/2-inch reflector, distinctly
perceived in 1890 seven of the duplicate objects noted at Milan,[996]
and the Lick observations, both of 1890 and of 1892, together with the
drawings made at Flagstaff and Mexico during the last favourable
oppositions of the nineteenth century, brought unequivocal confirmation
to the accuracy of Schiaparelli's impressions.[997] Various conjectures
have been hazarded in explanation of this bizarre appearance. The
difficulty of conceiving a physical reality corresponding to it has
suggested recourse to an optical rationale. Proctor regarded it as an
effect of diffraction;[998] Stanislas Meunier, of oblique reflection
from overlying mist-banks;[999] Flammarion considers it possible that
companion-canals might, under special ci