6 PRESIDENTIAL ADDRHSS. 
probably, to a reaction against the excesses of the Greek 
Mythologists. That the truth of none of these philosophies 
was self-evident is shown by the fact that, in the classical 
world, all of them flourished together, and highly cultivated 
men could be found among the Polytheists, the Pantheists, 
the Theists, and the Atheists. 
At last science awoke from its long sleep, and began to 
study with care the material phenomena of the Universe. 
Scientific observations commenced with the Chaldeans and 
early Greeks; but it was a dreamy kind of science, confined 
toafew. The spirit of inquiry was not thoroughly aroused 
until the bold navigators of the fifteenth and sixteenth 
centuries sailed round the world, and demolished the old 
dogma that the earth was a flat disc, with Jerusalem in its 
centre. Then the invention of the printing press spread 
the news far and wide, and from that time forwards science 
took an important position in the world. 
Long before this, however, the idea of law and order in 
Nature had been gradually growing. The wonders of the 
thunderstorm, of eclipses, even of the rainbow, had been 
explained as the result of physical laws, and the consequence 
was that the belief in the crude Polytheism of the ancients 
had been destroyed. 
The advance of scientific knowledge was at first very slow, 
until, in the seventeenth century, the great improvements 
which were made in mathematical analysis, as well as the 
invention of the telescope, enlarged men’s ideas enormously. 
and added vastly to their powers of observation and reason- 
ing. Before the century was over, the size of the earth had 
been ascertained with tolerable accuracy, and the law of 
universal gravitation had been discovered. In the eighteenth 
century, great progress was made in the experimental 
sciences of physics and chemistry. Electricity was detected, © 
as, also, was oxygen, and this laid the foundation of modern 
chemistry. Instruments of precision for weighing and 
measuring were invented, and, at the end of the century, 
not only was the distance of the sun approximately ascer- 
tained, but it was proved that matter was not destroyed 
when it was burnt, but only rendered invisible. The dis- 
covery that matter was indestructible led, in the nineteenth 
century, to the further discovery that the physical forces 
are so correlated that one can be changed into another. 
And, at last, it was definitely proved that energy was as 
indestructible as matter; that it was not lost when it was no 
longer exhibited, but had merely passed into the potential 
or invisible state. 
