“The only method of avoiding these inconveniences is to employ the cares and attentions, above mentioned. It is indeed unpleasant and very difficult continually to stop in the midst of the most interesting researches, and to employ much valuable time in cleaning and arranging vessels and attaching labels. These employments are capable of cooling and retarding the progress of genius, and are tedious and disgusting; but they are nevertheless necessary. Those persons whose fortunes enable them to have an assistant operator, on whose accuracy and intelligence they can depend, avoid many of these disagreeable circumstances; but they ought nevertheless to attend to the execution of these things. We cannot depend too much on ourselves in these matters, however minute, on account of their consequences. This becomes even indispensable when the experiments are to be kept secret, at least for a time, which is very common and often necessary in chemistry. “When new researches and inquiries are made, the mixtures, results, and products of all the operations ought to be kept a long time well ticketed and noted. It frequently happens that at the end of some time these things present very singular phenomena, which would never have been suspected. There are many beautiful discoveries in chemistry which were made in this manner, and certainly a much greater number which have been lost, because the products have been thrown away too hastily, or because they could not be recognised after the changes which happened to them.” The uses of equivalents, and the method of employing Dr. Wollaston’s scale, form the subject of the twenty-second section of Mr. Faraday’s book; and of the concluding sections, the twenty-third contains a quantity of miscellaneous remarks, and the twenty-fourth is appropriated to “a course of inductive and instructive practices;” that is, to a selection of minute instructions respecting the use of instruments, and the performance of operations.