204 Mr. C. Tomlinson's Experiments on the Electrical Fly, 



Bcccaria, in his treatise* published in 1771, represents the 

 fly in the form of an Italian /S y , but makes two mistakes as to its 

 inventor. He says (p. 331), "Points at the same time that 

 they drive the air forwards are themselves driven back. Mon- 

 sieur Jallambert [he means Jallabert] was the first who observed 

 this repercussion of points, which the Abbe Nollct afterwards 

 found to be uncertain." 



Now it is quite true that M. Jallabert of Geneva was the first 

 to observe the different effects produced by presenting a sharp 

 and a round point to a charged conductor; and in 1748 he 

 showed the experiment to the Abbe Nollet, who was not satis- 

 fied as to the constancy of the result; but neither in Jallabert' s 

 collected Essays f nor in any of Nollet' s numerous works, have 

 I been able to find any reference to the electric fly or tourniquet; 

 and it is not to be imagined but that so eager an experimen- 

 talist and so popular a lecturer as Nollet would have made 

 much of this elegant toy had he been acquainted with it. He 

 performed a number of experiments on the action of points, and 

 addressed one of his letters J to Franklin, stating Jallabert' s 

 experiments, his own, and his reasons for differing from some of 

 Franklin's conclusions. Even in his later work§ I find no 

 mention of the fly ; but there is a good deal about points, and 

 the engraving opposite page 378 represents the action of points 

 in various forms of brush. 



But to return to Beccaria. He says (page 338), " The cele- 

 brated question why points drive the air forwards, whatever the 

 direction of the fluid, is reduced to the general fact that the 

 electricity forces in contrary directions (or to opposite sides) the 

 resistances through which it passes ; because whether the elec- 

 tric fluid enter or escape, it not only drives fomvard the air, hut 

 drives back the points also " \\ . He has just related the experiment 

 of discharging a Leyden jar through a quire of paper, whereby a 

 burr is produced on both sides ; and from this and other expe- 

 riments draws a general conclusion as to the expansive force of 

 electricity. 



A few years later Cavallo makes the motion of the fly to 

 depend " upon the repulsion existing between bodies possessed of 

 the same electricity ; for whether the fly is electrified positively 

 or negatively, the air opposite to the points of the wires (on 



* Elettricismo Artificiale. 4to. Torino, 1771. 



\ Experiences sur VElectricite. 8vo. Geneva, 1748. 



% Lettres sur VElectricite. 12mo. Paris, 1764-6/. See vol. i. p. 124. 



§ Lemons de Physique, vol. vi. (1771). 



|| " II fuoco elettrico spinge in parti contrarie le resistenze, per le quali 

 tragitta ; perciocche o che il fuoco elettrico entri, ovvero che esca, non solo 

 spinge il venticello, ma retropinge anche le punte." 



