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] “Should it hereafter be discovered to be compound, and even to contain oxygen, this name can imply no error, and cannot necessarily require a change.” [H] [From χλωρος.] As the actual facts and arguments on which Davy based his views are seldom set forth in text-books, or presented to the student by teachers, it may be desirable to give a detailed account of his famous memoir. He begins by saying:-- “The illustrious discoverer of the oxymuriatic acid considered it as muriatic acid freed from hydrogen; and the common muriatic acid as a compound of hydrogen and oxymuriatic acid; and on this theory he denominated oxymuriatic acid dephlogisticated muriatic acid. “M. Berthollet, a few years after the discovery of Scheele, made a number of important and curious experiments on this body; from which he concluded that it was composed of muriatic acid and oxygen; and this idea for nearly twenty years has been almost universally adopted.”