anals' of Mars are not accepted by an astronomer of
equal knowledge and still wider experience. Yet Professor Pickering's
alternative view is more a suggestion than an explanation, because there
is no attempt to account for the enormous length and perfect
straightness of the lines on Mars, so different from anything that is
found either on our earth or on the moon. There must evidently be some
great peculiarity of structure or of conditions on Mars to account for
these features, and I shall now attempt to point out what this
peculiarity is and how it may have arisen.

_The Meteoritic Hypothesis._

During the last quarter of a century a considerable change has come over
the opinions of astronomers as regards the probable origin of the Solar
System. The large amount of knowledge of the stellar universe, and
especially of nebulae, of comets and of meteor-streams which we now
possess, together with many other phenomena, such as the constitution of
Saturn's rings, the great number and extent of the minor planets, and
generally of the vast amount of matter in the form of meteor-rings and
meteoric dust in and around our system, have all pointed to a different
origin for the planets and their satellites than that formulated by
Laplace as the Nebular hypothesis.

It is now seen more clearly than at any earlier period, that most of the
planets possess special characteristics which distinguish them from one
another, and that such an origin as Laplace suggested--the slow cooling
and contraction of one vast sun-mist or nebula, besides presenting
inherent difficulties--many think them impossibilities--in itself does
not afford an adequate explanation of these peculiarities. Hence has
arisen what is termed the Meteoritic theory, which has been ably
advocated for many years by Sir Norman Lockyer, and with some
unimportant modifications is now becoming widely accepted. Briefly, this
theory is, that the planets have been formed by the slow aggregation of
solid particles around centres of greatest condensation; but as many of
my readers may be altogether unacquainted with it, I will here give a
very clear statement of what it is, from Professor J.W. Gregory's
presidential address to the Geological Section of the British
Association of the present year. He began by saying that these modern
views were of far more practical use to men of science than that of
Laplace, and that they give us a history of the world consistent with
the actual