accompanied by a brilliant light. One may multiply this phenomenon so
far as to destroy a city or an army." Anticipating the use of even motor
boats and automobiles driven by gasoline, this thirteenth century
scientist wrote: "Art can construct instruments of navigation such that
the largest vessels governed by a single man will traverse rivers and
seas more rapidly than if they were filled with oarsmen. One may also
make carriages which, without the aid of any animal, will run with
remarkable swiftness." This man whose clarity of vision anticipated
those discoveries of the nineteenth century, left three disciples after
him,--John of Paris, William of Mara and Gerard Hay--who followed their
master's methods, especially of testing by observation and by careful
searching of authorities, every proposition that came up for study.

Perhaps the most striking argument in favor of the experimental attitude
of Dante's century is that afforded by certain facts in the history of
medicine of that epoch. Then surgery began to make vast strides. Pagel,
regarded in our time as the best informed writer on the history of
medicine, has this to say of the surgery in Dante's age. "The stream of
literary works on surgery flows richer during this period. While
surgeons are far from being able to emancipate themselves from the
ruling pathological theories, there is no doubt that in one department,
that of manual technics, free observation came to occupy the first place
in the effort for scientific progress. Investigation is less hampered
and concerns itself with practical things and not with artificial
theories. Experimental observation was in this not repressed by an
unfortunate and iron-bound appeal to reasoning." (The Popes and Science,
p. 172.)

As to medical practice in the thirteenth century, interesting data are
furnished by the Bulletin of Johns Hopkins Hospital and the Journal of