Davy is here seen at his best. He is bold and yet wary, and as dexterous as trenchant; so confident is he in the strength of his position that he casts aside every argument that might tell in his favour, unless it is based on the most unimpeachable evidence. It is difficult to know what to admire most--the clearness of perception, the precision of the statement, the strictness of the logic, the aptness of the illustration, or the argumentative skill with which the whole is marshalled and presented. As a piece of induction, the memoir is a model of its kind, and as an exercise in “the scientific use of the imagination” it has few equals. Most scientific papers will stand a considerable amount of winnowing, and there is no assay-master more scrupulously strict than Time. “The more a science advances, the more it becomes concentrated in little books,” says Leibnitz; but the most fastidious of critics might read and re-read this work without wishing to omit or amend a sentence.
Every chemical student to-day is told that the elementary nature of chlorine was first _demonstrated_ by Davy, and if the student is informed what Davy meant by the term “element,” the statement is not incorrect. What, however, Davy actually did was to demonstrate that the substance called oxymuriatic acid contained no oxygen; that it was a peculiar substance which “has not as yet been decompounded,” and therefore is “elementary as far as our knowledge extends.” The very character of the name which he suggested indicates this cautious and philosophical view. In making the suggestion, he says:--
“To call a body which is not known to contain oxygen and which cannot contain muriatic acid, oxymuriatic acid, is contrary to the principles of that nomenclature in which it is adopted; and an alteration of it seems necessary to assist the progress of discussion, and to diffuse just ideas on the subject. If the great discoverer of this substance [Scheele, who first observed it in 1774] had signified it by any simple name, it would have been proper to have recurred to it; but, _dephlogisticated marine acid_ is a term which can hardly be adopted in the present advanced era of the science.
“After consulting some of the most eminent chemical philosophers in this country, it has been judged most proper to suggest a name founded upon one of its obvious and characteristic properties--its colour, and to call it _chlorine_, or _chloric_ gas.[H]