Note 19 — SECTION IV. HIS METHOD OF WORKING.

Since the publication of the first edition I have been struck with how precisely his practice corresponded with his precept in the introduction to his book on "Chemical Manipulation:"—"When an experiment has been devised, its general nature and principles arranged in the mind, and the causes to be brought into action, with the effect to be expected, properly considered, then it has to be performed. The ultimate objects of an experiment, and also the particular contrivance or mode by which the results are to be produced, being mental, there remains the mere performance of it, which may properly enough be expressed by the term manipulation.

"Notwithstanding this subordinate character of manipulation, it is yet of high importance in an experimental science, and particularly in chemistry. The person who could devise only, without knowing how to perform, would not be able to extend his knowledge far, or make it useful; and where every doubt or question that arises in the mind is best answered by the result of an experiment, whatever enables the philosopher to perform the experiment in the simplest, quickest, and most direct manner, cannot but be esteemed by him as of the utmost value."