Yet another story is told of a grave old gentleman who once waited upon Faraday that he might show to him "a new law of physics." The gentleman asked for a jug of water and a tumbler; they were brought, and he then produced a cork. "You will be pleased to observe," he then said, "how persistently this cork clings to the side of the glass when the vessel is half-filled."
"Just so," replied the professor.
"But now," continued the discoverer of a new law of physics, "mark what happens when I fill the glass to the brim. There! you see the cork flies to the centre—positively repelled by the sides!"
"Precisely so," answered Faraday in an amused tone, which showed that the "new law" was more familiar to him than to his visitor, who, somewhat abashed, said, "Pray, how long have you known this?" "Oh, ever since I was a boy," was the reply; but the innate kindliness of his nature must show itself even in such a case, for, seeing the old gentleman's disappointed look, he added that he was not to be grieved, he might possibly some day alight upon something really new.
The last course of Faraday's Juvenile Lectures—on "The Chemical History of a Candle"—has been referred to once or twice. These lectures are indeed of very great interest, not only in themselves as chemical illustrations, but as being part of Professor Faraday's best known works, and the only juvenile lectures of his which are obtainable in the form of a book. The way in which he introduced his subject will show us how simple, and yet how explicit he was in explaining to his young audience the phenomena which he brought before them.
"I purpose," he said, to quote the beginning of the initial lecture of the series of six, "in return for the honour you do us by coming to see what are our proceedings here, to bring before you in the course of these lectures, the chemical history of a candle. I have taken this subject on a former occasion, and were it left to my own will, I should prefer to repeat it almost every year—so abundant is the interest that attaches itself to the subject, so wonderful are the varieties of outlet which it offers into the various departments of philosophy. There is not a law under which any part of this universe is governed which does not come into play, and is touched upon in these phenomena. There is no better, there is no more open door by which you can enter into the study of natural philosophy, than by considering the physical phenomena of a candle. I trust, therefore, I shall not disappoint you in choosing this for my subject rather than any newer topic, which could not be better, were it even so good.
"And before proceeding, let me say this also—that though our subject be so great, and our intention that of treating it honestly, seriously, and philosophically, yet I mean to pass away from all those who are seniors amongst us. I claim the privilege of speaking to juveniles as a juvenile myself. I have done so on former occasions—and, if you please, I shall do so again. And though I stand here with the knowledge of having the words I utter given to the world, yet that shall not deter me from speaking in the same familiar way to those whom I esteem nearest to me on this occasion.
"And now, my boys and girls, I must first tell you of what candles are made. Some are great curiosities. I have here some bits of timber, branches of trees particularly famous for their burning. And here you see a piece of that very curious substance taken out of some of the bogs in Ireland, called candlewood—a hard, strong, excellent wood, evidently fitted for good work as a resister of force, and yet withal burning so well that where it is found they make splinters of it, and torches, since it burns like a candle, and gives a very good light indeed. And in this wood we have one of the most beautiful illustrations of the general nature of a candle that I can possibly give. The fuel provided, the means of bringing that fuel to the place of chemical action, the regular and gradual supply of air to that place of action—heat and light—all produced by a little piece of wood of this kind, forming, in fact, a natural candle.
"But we must speak of candles as they are in commerce. Here are a couple of candles commonly called dips. They are made of lengths of cotton cut off, hung up by a loop, dipped into melted tallow, taken out again and cooled, then re-dipped until there is an accumulation of tallow round the cotton. In order that you may have an idea of the various characters of these candles, you see these which I hold in my hand—they are very small and very curious. They are, or were, the candles used by miners in coal mines. In olden times the miner had to find his own candles; and it was supposed that a small candle would not so soon set fire to the fire-damp in the coal mines as a larger one; and for that reason, as well as for economy's sake, he made candles of this sort—twenty, thirty, forty, or sixty to the pound. They have been replaced since then by the steel-mill, and then by the Davy lamp, and other safety lamps of various kinds. I have here a candle that was taken out of the Royal George, it is said, by Colonel Pasley. It has been sunk in the sea for many years, subject to the action of salt water. It shows you how well candles may be preserved; for though it is cracked about and broken a good deal, yet, when lighted, it goes on burning regularly, and the tallow resumes its natural condition as soon as it is fused."
We have not space to quote further from these delightful lectures, which however, as I have said earlier, can be got in a little volume by themselves. These lectures were, as indeed were most of Faraday's lectures, beautifully illustrated with a large number of experiments.