Philadelphia--a work to which we have been mainly indebted
in drawing up this article.

In the early part of the French revolutionary war, the _savants_ of
France, ambitious of bringing to the aid of the Republic all the
resources of science, strongly recommended the introduction of balloons,
as an effectual means of reconnoitring the armies of their enemies. From
the advantages it seemed to promise, the recommendation was instantly
acted on by the government, which established an aeronautic school at
Meudon, near Paris. The management of the institution, which was
conducted with systematic precision, and concealed with the utmost care
from the allied powers, was committed to the most eminent philosophers
of Paris. Gyton Morveau, a celebrated French chemist, and M. Contel,
superintended the operations. Fifty military students were admitted for
training. A practicing balloon of thirty-two feet in diameter was
constructed, of the most durable materials, and inflated with hydrogen
gas. It was kept constantly full, so as to be at all times ready for
exercise; and, to make it stationary at any given altitude, it was
attached to windlass machinery. Balloons were speedily prepared by M.
Contel for the different branches of the French army; the _Entreprenant_
for the army of the north, the _Celeste_ for that of the Sambre and
Meuse, the _Hercule_ for that of Rhine and Moselle, and the _Intrepide_
for the memorable army of Egypt. The victory which the French achieved
over the Austrians, on the plains of Fleurus, in June, 1794, is ascribed
to the observations made by two of their aeronauts. Immediately before
the battle, M. Contel and an adjutant-general ascended twice in the
war-balloon _Entreprenant_, to reconnoitre the Austrian army, and
though, during their second aerial _reconnaissance_ they were discovered
by the enemy, who sent up after them a brisk cannonade, they quickly
rose above the reach of danger, and, on descending, communicated such
information to their general, as enabled him to gain a speedy and
decisive victory over the Austrians.

The balloon was also at an early period taken advantage of for making
scientific experiments in the elevated regions of the atmosphere. With
the view of ascertaining the force of magnetic attraction, and of
examining the electrical properties and constitution of the atmosphere
at great elevations, two young, enthusiastic French philosophers, MM.
Biot and Gay Lussac, proposed to make