M. Rouelle, an eminent French chemist, was not the most cautious of operators. One day, while performing some experiments, he said to his auditors: "Gentlemen, you see this cauldron upon the brazier; well, if I were to cease stirring for one moment, an explosion would ensue, that would blow us all into the air." The audience had scarce had time to reflect on this comfortable piece of information, when the operator actually did forget to stir, and his prediction was amply verified. The explosion took place with a terrible crash; all the windows of the laboratory were smashed to pieces, and two hundred auditors were whirled away into the garden. Fortunately, no one received any serious injury, the chief violence of the explosion having been in the direction of the chimney. The demonstrator himself marvellously escaped without further harm than the loss of his wig.—A certain Scotch Professor—not of the present generation—as remarkable for the felicity of his experimentation as Rouelle could be for his failures, was once performing an experiment with some combustible materials, when the mixture exploded, and the phial which he held in his hand flew into a thousand pieces. "Gentlemen," said the Doctor to his students, with the most unaffected gravity, "I can assure you that I have performed this experiment often with the same phial, and never knew it break in my hands before." The simplicity of this somewhat superfluous assurance gave rise to a general laugh, in which the Professor, instantly discerning the cause of it in his own excellent Irishism, most heartily joined.