ut how was he to find a body at a sufficient distance?
He had no balloon? and even if he had, he knew that any height to
which he could attain would be too small to enable him to solve his
problem. What did he do? He fixed his thoughts upon the moon;--a
body 240,000 miles, or sixty times the earth's radius, from the
earth's centre. He virtually weighed the moon, and found that weight
to be 1/3600th of what it would be at the earth's surface. This is
exactly what his theory required. I will not dwell here upon the
pause of Newton after his first calculations, or speak of his
self-denial in withholding them because they did not quite agree with
the observations then at his command. Newton's action in this matter
is the normal action of the scientific mind. If it were otherwise--if
scientific men were not accustomed to demand verification--if they
were satisfied with the imperfect while the perfect is attainable,
their science, instead of being, as it is, a fortress of adamant,
would be a house of clay, ill-fitted to bear the buffetings of the
theologic storms to which it is periodically exposed.

Thus we see that Newton, like Torricelli, first pondered his facts,
illuminated them with persistent thought, and finally divined the
character of the force of gravitation. But, having thus travelled
inward to the principle, he reversed his steps, carried the principle
outwards, and justified it by demonstrating its fitness to external
nature.

And here, in passing, I would notice a point which is well worthy of
attention. Kepler had deduced his laws from observation. As far back
as those observations extended, the planetary motions had obeyed these
laws; and neither Kepler nor Newton entertained a doubt as to their
continuing to obey them. Year after year, as the ages rolled, they
believed that those laws would continue to illustrate themselves in
the heavens. But this was not sufficient. The scientific mind can
find no repose in the mere registration of sequence in nature. The
further question intrudes itself with resistless might, Whence comes
the sequence? What is it that binds the consequent to its antecedent
in nature? The truly scientific intellect never can attain rest until
it reaches the _forces_ by which the observed succession is produced. It
was thus with Torricelli; it was thus with Newton; it is thus
pre-eminently with the scientific man of to-day. In common with the
most ignorant, he shares the