The researches of Sir John Herschel have been principally directed to the investigation of the physical laws which regulate the chemical changes we have been considering. His analyses of the prismatic spectrum have been most complete, and, as far as they have been carried out, go to prove the operation of forces other than those with which we are acquainted.
At the same time, however, as this philosopher has been engaged in investigations of this high order, he has, from the multitude of his experiments, been successful in producing several processes of great beauty. There are not any which are to be regarded as peculiarly sensitive—they are indeed for the most part rather slow—but the manipulation required is of the easiest character, and the results are most curious and instructive.
The philosophy which is for ever united with the scientific investigations of Sir John Herschel, is too valuable to be omitted from any description of the processes which he recommends ; the following quotations are therefore taken from his communi-cation to the Royal Society, and linked together by my own remarks in such a manner as it is hoped will be most easily understood by the unscientific amateur.