434 PHILOSOPHICAL TRANSACTIONS. [aNNO 1753. 



Lf^Il. Observations on the Electricity of tlie Air, made at the Chateau de Main- 

 tenon, during June, July, and October, 1753 ; being Part of a Letter Jrom 

 the Abbe Mazeas, F. R. S. to the Rev. S. Hales, D. D., F. R. S. Translated 

 from the French by James Parsons, M. D., F. R. S. p. 377. 



June 14, M. Mazeas accompanied the Marechal de Noailles to his castle of 

 Maintenon. At his arrival, he set up an apparatus, consisting of an iron wire 

 370 feet long, raised to 90 feet above the horizon. It came down from a very 

 high room in the castle, where it was fastened to a silken cord 6 feet long, and 

 was carried from thence to the steeple of the town ; where it was likewise fastened 

 to another silken cord of 8 feet long, and sheltered from rain ; and a large key 

 was suspended by the end of this wire, to receive the electrical fluid. 



Observ. 1. From June 17, the time of beginning his experiments, the elec- 

 tricity of the air was sensibly felt every day, from sun-rise, to 7 or 8 in the 

 evening: except in moist weather, when he could perceive no signs of electricity. 

 In dry weather, the wire attracted minute bodies, at no greater distance than 3 

 or 4 lines. He constantly observed that, in weather void of storms, the electri- 

 city of a piece of sealing-wax of 2 inches long, was above twice as strong as 

 that of the air. Hence it would seem that, in weather of equal driness, the 

 electricity of the air is always equal. 



Observ. 1. When he grasped the wire closely in his hand, the electricity ceased 

 instantly, and did not recover till 3 or 4 minutes after; whereas, during a storm 

 we could deprive the wire of its electricity only for a moment; for it immediately 

 returned with the same vigour. Hence it appears that the common electricity of 

 the air has but a slow motion. 



Observ. 3. He endeavoured to increase the electricity of the wire, by the addi- 

 tion of a 2d, which communicated with an electrical magazine, composed of 

 pieces of iron, tin plates, gilt paper, and such like, sustained by silken cords; 

 and he observed, I . That the electrical fluid did not even then act with any more 

 strength on minute bodies presented to the wire. 2. That in depriving this ma- 

 gazine of its electricity, it seemed to return the more slowly the more consider- 

 able the magazine was ; whereas the contrary happens during a storm . This 

 slowness, with which the common electricity of the air is propagated, made him 

 despair of finding means capable of rendering its motion sensible. 



Obs. 4. — It did not appear that hurricanes and tempests increase the electricity 

 of the air, when they are not accompanied with thunder : for during 3 days of a 

 very violent continual wind in the month of July, he was obliged to put the dust 

 within 4 or 5 lines of the conductor, before any sensible attraction could be per - 

 ceived. The direction of the winds, whether east, west, north, or south, does 



