130 ATMOSPHERIC ELECTRICITY. 



repelling power was augmented in proportion as the drops in- 

 creased. 



On this occasion, M. Romayne was the first who made an 

 elegant experiment, to shew, tlfat the diminution of surface 

 increases the intensity of electricity in bodies. He found, by 

 repeated trials, that a piece of flannel, silk, &c. excited and 

 suddenly twisted, not only struck at a greater distance than 

 before, but sometimes emitted parcels of fire into the air. 

 And from this he infers, that the electricty of vapour, when 

 not in contact with the earth, ought to increase by condensa- 

 tion. This is still farther confirmed by the experiments of 

 Volta and of Bennet, on the electricity of vapour*. 

 Sudden chang- At other times, M. Romayne made use of a tapering tube of 

 es of deem- t ; n ^ twenty feet long, and ending in a point, insulated, and 



city, which . , _ . , ' - , 



might be ex- projecting upwards out of a window. He took rn^ice of that 

 plained byedr- uncertainty and frequent change in the electricity of clouds, 

 servations. ° which was before remarked by Dr. Franklin and ethers ; and, 

 after several ingenious observations, he expresses his wish, that 

 two or more persons, at a sufficient distance, would correspond 

 by signals, indicating positive electiicity by a red flag, and nega- 

 tive by a blue ; as it is highly probable that much more satisfac- 

 tory knowledge would be thus obtained, respecting the electri- 

 city of the clouds, thunder, &c. than any single observer could 

 acquire. 



The observations of Mr. Henley f tend to corroborate those 

 of Mr. Romayne, but do not lead to any further conclusions. 

 General fact*. I now proceed in the enumeration of general facts, or the 



propositions of Beccaria. 



.Single clouds g. In clear weather, when a low cloud, considerably distant 



fntensity in the f>'°™. any other, happens to pass slowly over the wire, the posi- 



wire. Separate tive electricity is usually much diminished, but is not rendered 



masses increase ne g at j ve . an( i^ w hen the cloud is gone, it returns to its former 



state. But, if numbers of whitish clouds, resembling locks of 



wool, continually uniting and separating, remain over the 



wire, so as to form a considerable extent, the positive ekctri- 



* And more fully by the condenser and well-known experiments, 

 made with Bennetts gold-leaf electrometer. 



T Ph. Trans, vol. C2. p. 145, and vol. G4. p. 422, 



cry 



