92 THE POPULAR SCIENCE MONTHLY. 



enjoyed, in his own student days, at Daventry. One of his pupils tells 

 us that 



"At the conclusion of his lecture, he always encouraged his students to ex- 

 press their sentiments relative to the subject of it, and to urge any objections to 

 what he had delivered, without reserve. It pleased him when any one com- 

 menced such a conversation. In order to excite the freest discussion, he occa- 

 sionally invited the students to drink tea with him, in order to canvass the sub- 

 jects of his lectures. I do not recollect that he ever showed the least displeas- 

 ure at the strongest objections that were made to what he delivered, but I dis- 

 tinctly remember the smile of approbation with which he usually received them : 

 nor did he fail to point out, in a very encouraging manner, the ingenuity or force 

 of any remarks that were made, when they merited these characters. His 

 object, as well as Dr. Aikin's, was, to engage the students to examine and decide 

 for themselves, uninfluenced by the sentiments of any other persons." 1 



It would be difficult to give a better description of a model teacher 

 than that conveyed in these words. 



From his earliest days, Priestley had shown a strong bent toward 

 the study of Nature ; and his brother Timothy tells that the boy put 

 spiders into bottles to see how long they would live in the same air 

 a curious anticipation of the investigations of his later years. At 

 Nantwich, where he set up a school, Priestley informs us that he 

 bought an air-pump, an electrical machine, and other instruments, in 

 the use of which he instructed his scholars. But he does not seem 

 to have devoted himself seriously to physical science until 1766, when 

 he had the great good fortune to meet Benjamin Franklin, whose 

 friendship he ever afterward enjoyed. Encouraged by Franklin, he 

 wrote a "History of Electricity," which was published in 1767, and 

 appears to have met with considerable success. 



In the same year, Priestley left Warrington to become the min- 

 ister of a congregation at Leeds ; and here, happening to live next 

 door to a public brewery, as he says 



" I at first amused myself with making experiments on the fixed air which I 

 found ready made in the process of fermentation. When I removed from that 

 house I was under the necessity of making fixed air for myself; and, one experi- 

 ment leading to another, as I have distinctly and faithfully noted in my various 

 publications on the subject, I by degrees contrived a convenient apparatus for 

 the purpose, but of the cheapest kind. 



" When I began these experiments I knew very little of chemistry, and had, 

 in a manner, no idea on the subject before I attended a course of chemical lect- 

 ures, delivered in the academy at Warrington, by Dr. Turner, of Liverpool. 

 But I have often thought that, upon the whole, this circumstance was no disad- 

 vantage to me ; as, in this situation, I was led to devise an apparatus and pro- 

 cesses of my own, adapted to my peculiar views ; whereas, if I had been pre- 

 viously accustomed to the usual chemical processes, I should not have so easily 

 thought of any other, and, without new modes of operation, I should hardly 

 have discovered any thing materially new." 2 



1 "Life and Correspondence of Dr. Priestley," by J. T. Rutt, vol. i., p. 50. 



2 "Autobiography," 100, 101. 



