All of us have red-letter days in our lives. Some, the practical men, have been successful in business; they have made money and hold their heads high in consequence. Others, the thinkers, have gained ideas; they have opened a new account in the ledger of nature and silently taste the hallowed joys of truth. One of my great days was that of my first acquaintance with oxygen. On that day, when my class was over and all the materials put back in their place, I felt myself grow several inches taller. An untrained workman, I had shown, with complete success, that which was unknown to me a couple of hours before. No accident whatever, not even the least stain of acid. It is, therefore, not so difficult nor so dangerous as the pitiful finish of the Saint-Martial lesson might have led me to believe. With a vigilant eye and a little prudence, I shall be able to continue. The prospect is enchanting. And so, in due season, comes hydrogen, carefully contemplated in my reading, seen and reseen with the eye of the mind before being seen with the eyes of the body. I delight my little rascals by making the hydrogen-flame sing in a glass tube, which trickles with the drops of water resulting from the combustion; I make them jump with the explosions of the thunderous mixture. Later, I show them, with the same invariable success, the splendours of phosphorus, the violent powers of chlorine, the loathsome smells of sulphur, the metamorphoses of carbon, and so on. In short, in a series of lessons, the principal non-metallic elements and their compounds are passed in review during the course of the year. The thing was bruited abroad. Fresh pupils came to me, attracted by the marvels of the school. Some more places were laid in the dining-hall; and the principal, who was more interested in the profits on his beans and bacon than in chemistry, congratulated me on this accession of boarders. [31] However, we must make it clear, without wishing in any way to belittle the importance or the magical results of chemistry, that the latter was not the only attraction of the young schoolmaster’s teaching, any more than it was the sole subject on his programme. Among the other subjects taught, one in especial had the power of interesting master and pupil alike: This was open-air geometry, practical surveying. The College had none of the necessary outfit; but, with my fat pay—seven hundred francs a year, if you please!—I could not hesitate over the expense. A surveyor’s chain and stakes, arrows, level, square, and compass were bought with my money. A microscopic graphometer, not much larger than the palm of one’s hand and costing perhaps five francs, was provided by the establishment. There was no tripod to it; and I had one made. In short, my equipment was complete.