MEMOIR OF PRIESTLEY. 141 



remained eleven years, up to the time of the disturbances which com- 

 pelled him to quit that city and determined him to seek a refuge in 

 the United States. Such is the brief yet complete outline of his pri- 

 vate life ; the history of his works, as it is more important, must be 

 more extended. 



The first of them were intended for the service of education, and an 

 English grammar, his earliest production, is still used in the schools 

 of Great Britain. His historic and geographic charts deserve to be 

 used everywhere for the ingenious manner in which they represent the 

 origin and fall of each State and the career of every celebrated man. 

 His lessons on history evince both the comprehension and knowledge 

 requisite for a profitable study of the revolutions of nations. Those 

 on oratory and criticism are recognized as useful guides to the exer- 

 cises of the young.* 



This didactic form was that which he still employed in his first 

 works on physics ; his histories, namely, of electricity and optics, and 

 kis elements of perspective. The history of electricity was judiciously 

 timed, for it appeared just when Franklin, by the boldness and suc- 

 cess of his investigations, had thrown the brightest lustre around this 

 interesting branch of physics, and as all that had been done up to 

 that date was here presented in a clear and concise form, it was trans- 

 lated into several languages and first drew some notice in foreign 

 countries to the name of its author. 



The ungrateful taslc, however, of recounting what had been done 

 by others was not long to limit the activity of Priestley. He proceeded 

 without loss of time to place himself in the line of j)hysical discoverers, 

 and it was chiefly by his researches into the difterent kinds of air that 

 he merited that title and established the most durable monument of his 

 own renown. 



It had long been known that many bodies give out air and that 

 others absorb it under certain circumstances. It had been observed 

 that the air of neglected privies and of the bottoms of wells, with that 

 evolved by fermentation, extinguishes light and destroys animal life. 

 A light air, also, had been observed in the interior of mines, floating 

 mostly about the vaults of the passages, and kindling sometimes with 

 fearful explosions. The former had received the name oi' Jixed smd 

 the latter that of infiamrnable air. They are the same which we now 

 call carbonic acid gas and carhuretted-liydrogen. Cavendish had 

 determined their specific gravity ; Black had ascertained that it is 

 the fixed air which renders the alkalies and lime efiervescent ; and 

 Bergman had not been backward in detecting its acid properties. 

 Such was the state of knowledge in these particulars when Priestley 

 laid hold of the matter and treated it with a felicity altogether peculiar 

 to himself. 



Happening to be lodged, at Leeds, next door to a brewery, he had 

 the curiosity to examine the fixed air which is exhaled from beer in 



* Referring to these productions, Lord Brougham remarks : •' It is difficult to imagme any- 

 thing more adventurous tiian tiie tutor of an academy afflicted with an incurable stutter, 

 and who devoted liis lime to tcaciiiug and theology, promulgating rules of eloquence to the 

 senators and lawyers of his country." 



