ace to stand on and I will move the world."
What he and others had learned concerning fluid pressure, or
concerning pulleys, levers, and other mechanical devices, had not been
lost by the Greeks and had been borrowed from them for full practical
use by the Romans. They knew how to lift huge weights, and how to hurl
heavy missiles by the artillery previously mentioned. Experiments had
been made at Alexandria in the use of steam-power, but had led to
nothing practical. It is obvious also from their buildings and works
of engineering, even without explicit statement, that they well
understood the distribution of weight and the laws of stability. The
laws of acoustics were understood with sufficient clearness to make
them applicable with success to theatres. In practical mensuration--a
daily necessity for men who were perpetually allotting lands or
marking out camps--the Romans were experts. In pure arithmetic the
contemporary world had made some considerable advance, such as in the
extraction of square-roots and cube-roots; but, as has been already
said, the Roman interest was virtually confined to such arithmetic or
mathematics as appeared to possess some bearing on actual use.

Of chemistry, in the modern scientific sense, the ancients knew almost
nothing. Empirically they were aware of certain properties exhibited
by substances, and could perform certain manipulations; but, like
moderns down to a very recent time, they had no real understanding of
the quantitative or qualitative relations of elements. Long ago Greek
philosophy, followed by the Epicurean school, had set forth an "atomic
theory," which on the surface is surprisingly like the modern chemical
hypothesis; but this contained strange and illogical features and had
no connection with actual practice. In this department the chief
proficiency of the world of this date lay in metallurgy, in which the
processes empirically discovered, chiefly by Egyptians and
Phoenicians, were closely similar to those now employed. They
thoroughly understood the smelting of ores, but could render no
scientific account of the processes. Botany was in a very crude
condition, scarcely extending beyond such knowledge as was required on
the one hand for farming and horticulture, and on the other for the
vegetable medicines used by contemporary physicians.

The doctoring of the time was also, of course, largely empirical, but
assuredly hardly more so than it was a century or so ago, and