ELECTRICITY 455 



The ill success of these experiments seems to me to 

 have arisen chiefly from the uncommon dampness of the 

 circumambient air, which had been observed by everybody 

 since we crossed the tropic, and is fully noticed in my 

 journal. By this solution alone can all the phenomena 

 that appeared be accounted for. 



Air charged with particles of damp is well known to be 

 of all others the greatest enemy to electricity. It im- 

 mediately attracts and dissipates all the electrical matter 

 which is collected by the machine, which therefore worked 

 faintly for a little while, till the damp was condensed on 

 the conductor, and chiefly on the surface of the glass phial, 

 and then ceased entirely. A small quantity was, however, 

 always noticeable upon the surface of the plate, even to the 

 end of the conductor. 



The phial, though charged as full as the machine would 

 fill it, even at the time of its best working, scarcely retained 

 the electrical matter at all, owing doubtless to the com- 

 munication made by the condensed damp between the 

 coating and the stopper of the phial ; this increased every 

 moment, so that at last it would not contain any electricity. 



The situation on board ship would not allow the use of 

 a fire to warm the whole machine, which should have been 

 done, and which would have been a great satisfaction, but 

 the motion of the ship, the distance of the galley from the 

 cabin, and the number of people who are constantly busy 

 there, made that impossible. 



The dampness of the air complained of here has not 

 been observed now for the first time. Piso, in his account 

 of the Brazils, mentioned it, and says that victuals which 

 have kept well before spoil immediately there. This there- 

 fore may account for the general opinion of electrical 

 machines failing to work when near the line, as the fault 

 could not be in my machine which worked remarkably well 

 in London, and fully as well as I expected in Madeira. 



25th October 1768, 17 miles south of the line Mr. 

 Green's machine. This was made by Watkins : the jar 

 was of glass 8 inches high and 7 Tdeep, coated with 



