in the reasoning of Anaxagoras. By scientific induction he passed
from observation to explanation. A new and most important element
was added to the science of astronomy.

Looking back from the latter-day stand-point, it would seem as if
the mind of the philosopher must have taken one other step: the
mind that had conceived sun, moon, stars, and earth to be of one
substance might naturally, we should think, have reached out to
the further induction that, since the moon is a sphere, the other
cosmic bodies, including the earth, must be spheres also. But
generalizer as he was, Anaxagoras was too rigidly scientific a
thinker to make this assumption. The data at his command did not,
as he analyzed them, seem to point to this conclusion. We have
seen that Pythagoras probably, and Parmenides surely, out there
in Italy had conceived the idea of the earth's rotundity, but the
Pythagorean doctrines were not rapidly taken up in the mother-
country, and Parmenides, it must be recalled, was a strict
contemporary of Anaxagoras himself. It is no reproach, therefore,
to the Clazomenaean philosopher that he should have held to the
old idea that the earth is flat, or at most a convex disk--the
latter being the Babylonian conception which probably dominated
that Milesian school to which Anaxagoras harked back.

Anaxagoras may never have seen an eclipse of the moon, and even
if he had he might have reflected that, from certain directions,
a disk may throw precisely the same shadow as a sphere. Moreover,
in reference to the shadow cast by the earth, there was, so
Anaxagoras believed, an observation open to him nightly which, we
may well suppose, was not without influence in suggesting to his
mind the probable shape of the earth. The Milky Way, which
doubtless had puzzled astronomers from the beginnings of history
and which was to continue to puzzle them for many centuries after
the day of Anaxagoras, was explained by the Clazomenaean
philosopher on a theory obviously suggested by the theory of the
moon's phases. Since the earth- like moon shines by reflected
light at night, and since the stars seem obviously brighter on
dark nights, Anaxagoras was but following up a perfectly logical
induction when he propounded the theory that the stars in the
Milky Way seem more numerous and brighter than those of any other
part of the heavens, merely because the Milky Way marks the
shadow of the earth. Of course the inference was wrong, so far as
the shadow of the earth is concerned; yet it contained a part
truth, the force of which was never fully recognized until the
time of Galileo. This consists in the assertion that the
brightness of the Milky Way is merely due to the glow of many
stars. The shadow- theory of Anaxagoras would naturally cease to
have validity so soon as the sphericity of the earth was proved,
and with it, seemingly, fell for the time the companion theory
that the Milky Way is made up of a multitude of stars.

It has been said by a modern critic[1] that the shadow-theory was
childish in that it failed to note that the Milky Way does not
follow the course of the ecliptic. But this criticism only holds
good so long as we reflect on the true character of the earth as
a symmetrical body poised in space. It is quite possible to
conceive a body occupying the position of the earth with
reference to the sun which would cast a shadow having such a
tenuous form as the Milky Way presents. Such a body obviously
would not be a globe, but a long-drawn-out, attenuated figure.
There is, to be sure, no direct evidence preserved to show that
Anaxagoras conceived the world to present such a figure as this,
but what we know of that philosopher's close-reasoning, logical
mind gives some warrant to the assumption--gratuitous though in a
sense it be-- that the author of the theory of the moon's phases
had not failed to ask himself what must be the form of that
terrestrial body which could cast the tenuous shadow of the Milky
Way. Moreover, we must recall that the habitable earth, as known
to the Greeks of that day, was a relatively narrow band of
territory, stretching far to the east and to the west.


Anaxagoras as Meteorologist

The man who had studied the meteorite of aegospotami, and been
put by it on the track of such remarkable inductions, was,
naturally, not oblivious to the other phenomena of the
atmosphere. Indeed, such a mind as that of Anaxagoras was sure to
investigate all manner of natural phenomena, and almost equally
sure to throw new light on any subject that it investigated.
Hence it is not surprising to find Anaxagoras credited with
explaining the winds as due to the rarefactions of the atmosphere
produced by the sun. This explanation gives Anaxagoras full right
to be called "the father of meteorology," a title which, it may
be, no one has thought of applying to him, chiefly because the
science of meteorology did not make its real beginnings until
some twenty-four hundred years after the death of its first great
votary. Not content with explaining the winds, this prototype of
Franklin turned his attention even to the tipper atmosphere.
"Thunder," he is reputed to have said, "was produced by the
collision of the clouds, and lightning by the rubbing together of
the clouds." We dare not go so far as to suggest that this
implies an association in the mind of Anaxagoras between the
friction of the clouds and the observed electrical effects
generated by the friction of such a substance as amber. To make
such a suggestion doubtless would be to fall victim to the old
familiar propensity to read into Homer things that Homer never
knew. Yet the significant fact remains that Anaxagoras ascribed
to thunder and to lightning their true position as strictly
natural phenomena. For him it was no god that menaced humanity
with thundering voice and the flash of his divine fires from the


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