MEMOIR OF PRIESTLEY. 143 



vegetables restore, and combustion alters. He named it depMogisti- 

 cated air. 



The other aeriform fluids which differed from the atmospheric air 

 had been found to extinguish lights: this caused them to burn with 

 a brighter flame and with wonderful rapidity. The others deprived 

 animals of life: in this they lived longer than in even the common 

 air, without need of renewing it, while their faculties seemed to acquire 

 from it a greater energy. For the instant it was imagined a new 

 means of existing, and perhaps of prolonging life, had been discov- 

 ered, or at least an assured remedy against the greater part of the 

 maladies of respiration. 



This hope has proved deceptive, but dephlogisticated air has not the 

 less remained one of the most brilliant discoveries of the eighteenth 

 century; it is this v^hich, under the name of oxygen, modern chemistry 

 regards as one of the most universal agents of nature. By its means 

 all combustion and calcination are effected ; it enters into the compo- 

 sition of all acids ; it is one of the elements of water, and the great 

 reservoir of fire ; to it we owe almost all the artificial heat which we 

 procure in common life and in the arts ; this it is which, in respira- 

 tion, gives to all animated bodies their natural warmth and furnishes 

 the material principle of their movements. The energy of different 

 kinds of animals is in proportion to the force of its action upon them, 

 and in the growth of vegetables there is no period when they do not 

 combine with or disengage it in different manners. In a word, 

 physics, chemistry, and physiology, both animal and vegetable, have 

 scarcely a phenomenon which they can entirely explain without the 

 element in question. 



What has been said is but a slight sketch of the most remarkable 

 discoveries of Priestley ; time forces us to neglect a multitude of others 

 which would of themselves furnish ample materials for the eulogy of 

 another man. Each of his experiments has proved fertile in conse- 

 quences, and it can scarcely be doubted that there are some of them 

 which only await a closer attention to become the germ of new and 

 important deductions. 



His labors, as might be expected, were received with general interest ; 

 his works translated into all languages, and his experiments repeated, 

 varied, and commented upon by the ablest inquirers. For his earlier 

 researches on phlogistic air the Royal Society had awarded him Cop- 

 ley's medal, which is bestowed for the most important physical labor 

 made public within the year, and which England regards as the 

 noblest prize of scientific merit. The Academy of Paris accorded him 

 a prize not less noble, and, because rarer, of more difficult attainment, 

 the place of one of its eight foreign associates ; an object of compe- 

 tition to all the scientists of Europe, and whose list of names, com- 

 mencing with those of Newton, Leibnitz and Peter the Great, has 

 never degenerated from that original splendor. 



Priestley saw with surprise this accumulation of honors and mod- 

 estly wondered at the multitude of precious truths which nature 

 seemed to have reserved for his sole discovery. He forgot that her 

 favors are never gratuitous, and that it' she had so freely disclosed her- 

 self, it was because he had known how to extort her answers by the 



