The great success of the Montgolfier balloons naturally threw the efforts of Monsieur Charles and the brothers Robert into the shade. Nevertheless those gentlemen had got hold of a better principle than their rivals; and, knowing this, they resolved to convince the sceptical by constructing another balloon. They wisely began by obtaining subscriptions to enable them to carry out their designs, and finally succeeded in making a globe formed of tiffany, covered with elastic varnish, which was twenty-eight feet in diameter. This they filled with hydrogen gas. Some idea of their difficulties and expenses may be gathered from the fact that the mere filling of the balloon required an apparatus which cost about 400 pounds sterling, one-half of which was expended on the production of the gas alone. The ascent of this balloon deserves to be regarded with special interest, because, besides being the first _hydrogen_ balloon which carried up human beings, it was the first in which scientific observations were made and recorded. Monsieur Charles was a lecturer on natural philosophy, and, like our own great aeronaut, Mr Glaisher, does not seem to have been content to produce merely a spectacle, but went up to the realms of ether with an intelligent and scientific eye; for we read of him recording the indications of the thermometer and barometer at different heights and under various conditions. There were many accidents and delays in the construction of this balloon; but at last, on the 1st December 1783, it was taken to the Tuileries and there filled with gas. The process was slow, as the gas had to be generated in large quantities by means of diluted sulphuric acid and iron filings put into wooden casks disposed round a large cistern, from which it was conveyed through water in long leaden pipes. To keep the impatient populace quiet, therefore, during the tedious operation, Montgolfier sent up one of his fire-balloons. At last, when it was sufficiently filled, Messieurs Charles and Robert stepped into the car, which was ballasted with sandbags, and the ropes were let go. It went up with slow and solemn motion, at the rate of about five miles an hour. "The car," writes a reporter of the day in language more inflated than the balloon itself, "ascending amidst profound silence and admiration, allowed, in its soft and measured ascent, the bystanders to follow with their eyes and hearts two interesting men, who, like demigods, soared to the abode of the immortals, to receive the reward of intellectual progress, and carry the imperishable name of Montgolfier. After the globe had reached the height of 2000 feet, it was no longer possible to distinguish the aerial navigators; but the coloured pennants which they waved in the air testified their safety and their tranquil feelings. All fears were now dissipated; enthusiasm succeeded to astonishment; and every demonstration was given of joy and applause."