Monsieur Roger, drawn out of his thoughts by this question, raised his head, looked at Miette, and said to her,—
"In the first place, do you know what water is?"
"No; but you were going to tell me."
"All right. The celebrated Lavoisier, after having shown that air is not a simple body, but that it is composed of two gases, next turned his attention to the study of water, which was also, up to that time, considered to be an element; that is, a simple body. He studied it so skilfully that he succeeded in showing that water was formed by the combination of two gases."
"Of two gases!—water?" cried Miette.
"Certainly, of two gases. One of these gases is oxygen, which we have already spoken of, and the other is hydrogen."
"Which we are going to speak of," added Miette.
"Of course," answered Monsieur Roger, "since you wish it. But it was not Lavoisier, however, who first discovered hydrogen. This gas had been discovered before his time by the chemists Paracelsus and Boyle, who had found out that in placing iron or zinc in contact with an acid called sulphuric acid, there was disengaged an air "like a breath." This air "like a breath" is what we now call hydrogen. Lavoisier, with the assistance of the chemist Meusnier, proved that it was this gas which in combining with oxygen formed water. In order to do this he blew a current of hydrogen into a retort filled with oxygen. As this hydrogen penetrated into the retort, he set fire to it by means of electric sparks. Two stop-cocks regulated the proper proportions of the oxygen and the hydrogen in the retort. When the combustion took place, they saw water form in drops upon the sides of the retort and unite at the bottom. Water was therefore the product of the combination of hydrogen with oxygen. The following anecdote is told in regard to this combination. A chemist of the last century, who was fond of flattery, was engaged to give some lessons to a young prince of the blood royal. When he came to explain the composition of water, he prepared before his scholar the necessary apparatus for making the combination of hydrogen and oxygen, and, at the moment when he was about to send the electric spark into the retort, he said, bowing his head,—
"'If it please your Royal Highness, this hydrogen and oxygen are about to have the honor of combining before you.'