10 INTERPRETATIONS OF NATURE. 
herself had so many times painted upon the moon dur- 
ing an eclipse, was understood ; the shadow was a mes- 
senger of light; a revelation of a truth; an appeal to 
reason. 
Del-Cano had completed the circumnavigation of the 
earth, and verified the fact that it was indeed spherical 
inform. Then the objective world, so greatly enlarged 
by the navigators of the age, ‘‘ began to assume a prepon- 
derating force over the mere creations of the mind.” 
New lands and seas with forms of life so strange and 
wonderful, new skies and stars filled the mind with an 
enthusiasm which found expression in the marvelous 
advance of mathematical and astronomical science in 
the seventeenth century, by which Copernicus was en- 
abled to remodel the Ptolemaic system, and Kepler to 
formulate the laws of planetary motions, while Newton, 
interpreting these laws, bound with the force of gravity 
the swinging atom and the rushing world. Alhazen had 
known this force as it applied to terrestrial matter, but 
it was the glory of Newton to see it holding the universe 
in the bonds of unity, and to determine the measure and 
method of its action. 
The telescope of Galileo brought to human vision 
worlds hitherto unknown, and the ‘‘discovery of Jupi- 
ter’s moons marks an important epoch in the history of 
celestial physics ;”’ for the shadow cast by the occultation 
of these moons became the revealing messenger of light’s 
velocity, and upon this knowledge depends ‘‘ the inter- 
pretation of the aberration ellipse of the fixed stars in 
which the great orbit of the earth in its annual course 
round the sun, is, as it were, reflected on the vault of 
heaven.” 
A century later, more powerful lenses broke the dim, 
blending light of nebulae into multitudes of glittering 
suns, while the spectroscope has gathered the waves of 
