ment even to his class, and several years elapsed before this
obvious property of hydrogen gas was applied to the elevation of
balloons."

Cavallo made the first practical attempts with hydrogen gas six years
later, but he only succeeded in causing soap-bubbles to ascend.

At last the art of aerial navigation was discovered in France, and in
1782 the first ascent was made. The triumph was achieved by Stephen and
Joseph Montgolfier, sons of a wealthy paper-maker who dwelt at Annonay,
on the banks of a rivulet which flows into the Rhone, not far from
Lyons.

These brothers were remarkable men. Although bred in a remote
provincial town, and without the benefit of a liberal education, they
were possessed in a high degree of ingenuity and the spirit of
observation. They educated themselves, and acquired an unusually large
stock of information, which their inventive and original minds led them
to apply in new fields of speculation. They were associated in business
with their father, a man who passed his quiet days like a patriarch
amidst a large family and a numerous body of dependants, until he
reached the advanced age of ninety-three.

Stephen devoted himself chiefly to the study of mathematics, Joseph to
chemistry; and they were accustomed to form their plans in concert. It
appears that they had long contemplated, with philosophical interest,
the floating and ascent of clouds in the air, and when they heard of or
read Cavendish's theories in regard to _different kinds of air_, it at
once struck them that by enclosing some gas lighter than the atmosphere
in a bag, a weight might be raised from the earth into the air.

The brothers Montgolfier were men of that vigorous stamp who act
promptly on receiving their convictions. At once they set about
experimenting, and constructed large bags of paper,--the substance which
naturally came readiest to their hands, and which appeared to them to be
best suited to their purpose. These were filled with hydrogen gas,
which raised them to the ceiling; but, owing to the escape of the gas
through the pores and cracks of the case, those embryo balloons
descended in a few minutes. Instead of varnishing the paper to prevent
the escape of the gas, and supposing, erroneously, that the fault lay in
the latter, they sought about for a new gas more suitable to the paper.
This they found, as they supposed, in the gas which resulted from the
combustion of wet straw and wool, which had an