"[I]f we consider how much more genius is requisite for the devising of an apparatus or method of research which is quite new than is needed for its indefinite extension and improvement, and if we further judge the experimenter of 1766, not by his successors of 1840 or 1850, but by his contemporaries, we shall not hesitate to assign a very high rank to Cavendish, as one of the earliest investigators of the chemical properties of the gases."