36 LOEWENFELD, Contributions to tJie History of Science. 



mixtures of this kind, that should have the same 

 property in any required degree, and it is very easy to 

 conceive that a most dangerous use might be made of 

 them. But whatever is capable of doing mischief is 

 likewise of doing good. . . . 



Joseph Priestley. 



It is rather difficult to understand the part of this 

 letter, which relates to the theoretical question. It shows 

 what difficulties the phlogiston theory had to encounter 

 if it tried to explain the presence of oxygen in substances 

 " which for anything that appeared had always been in 

 the bowels of the earth." The last part of the letter is 

 interesting, as it shows how soon Priestley thought of 

 technical use of oxygen, a point to which he recurs at 

 various times in his writings. 



Birmingham and its surroundings was the seat of a 

 great number of men of learning and of prominent literary 

 merits, among whom may be mentioned Erasmus Darwin 

 (the grandfather of Charles Darwin, a peculiar but certainly 

 very remarkable man), James Watt, and his partner, 

 Matthew Boulton, William Murdock, the inventor of the 

 system of lighting by gas, Thomas Day, the eccentric 

 author of ' Sandford and Merton,' Richard Lovell Edge- 

 worth (whose daughter, Maria Edgeworth, is well known 

 as the author of novels and tales for children, in some 

 of which she collaborated with her father), who intro- 

 duced into England a system of optic telegraphy. These 

 met^. and several others met at the house of one of 

 them for dinner every month, on the Monday nearest 

 the full moon, so as to have the benefit of its light 

 when returning home. From this they derived their name 

 ' Lunar Society."*'* 



^•~' More about the 'Lunar Society' is to be found in Bolton, I.e., 

 pp. 195-219- 



