JOSEPH PRIESTLEY. 107 



The first outcome of Priestley's chemical work, pub- 

 lished in 1772, was of a very practical character. He 

 discovered the way of impregnating water with an ex- 

 cess of " fixed air," or carbonic acid, and thereby pro- 

 ducing what we now know as " soda water " a service 

 to naturally, and still more to artificially, thirsty souls, 

 which those whose parched throats and hot heads are 

 cooled by morning draughts of that beverage, cannot 

 too gratefully acknowledge. In the same year, Priestley 

 communicated the extensive series of observations which 

 his industry and ingenuity had accumulated, in the course 

 of four years, to the Royal Society, under the title of 

 "Observations on Different Kinds of Air" a memoir 

 which was justly regarded of so much merit and im- 

 portance, that the Society at once conferred upon the 

 author the highest distinction in their power, by award- 

 ing him the Copley Medal. 



In 1771 a proposal was made to Priestley to accom- 

 pany Captain Cook in his second voyage to the South 

 Seas. He accepted it, and his congregation agreed to 

 pay an assistant to supply his place during his absence. 

 But the appointment lay in the hands of the Board of 

 Longitude, of which certain clergymen were members ; 

 and whether these worthy ecclesiastics feared that Priest- 

 ley's presence among the ship's company might expose 

 his Majesty's Sloop Resolution to the fate which afore- 

 time befell a certain ship that went from Joppa to 

 Tarshish; or whether they were alarmed lest a Socin- 

 ian should undermine that piety which, in the days of 



