421 EUBi-ica! Machine eperailng hy the FriBioti of Sm, 



The conductor S Is fufpended by filk ftrings, faftened to the uprights of the machine by 

 the hooks and rings i i : its fituation is^ parallel to the cylinders G, H, and equidiftant from 

 each. The aflion of this machine is as follows : The cylinder H is moved rapidly on its 

 'axis by means of the handle, and the cylinder G moves of courfe in the fame direction on 

 the two extremities of its axis, provided the tafFety K, L, be properly flretched. This ten- 

 fion is eafily obtained ; becaufe the crofs pieces to which the uprights C, D, and E, F, are 

 fixed, may be moved nearer or further from each other, and faftened by means of the 

 fcrews a b and c d, which pafs through holes cut in the direction of the table. 



The rotation of the cylinders neceflarily producing a circulation of the tafFety, it muft 

 confequently be rubbed in its paflage between the tin tubes covered with cat's (kin at M 

 and N ; and by this friction it obtains what is called the negative eledtricity, which is com- 

 municated from both parts of the filk to the common condu£lor S. But it may be made to 

 eleflrify pofitively, by removing the rubbers to the middle of the filk, fo that the prime 

 Condu<Sor may communicate with them : or, if the two cufliions be removed to half the 

 diflance between the revolving cylinders and the prime condu6lor, pofitive and negative 

 electricity may be had at the fame time, the rubbers being in a negative ftate, and the 

 prime conduiStor in a pofitive ftate. 



The advantages of a machine of this conftru£tion beyond thofe of glafs are ftated by the 

 inventor to be, i. It is not brittle in any part. 2. Its excitation is more Itcady, becaufe it 

 requires no amalgam 3. Its dimenfions have no limit. 



The power of excitation in this way appears to have been very confiderable. The fa£l* 

 are not related with fo much detail as could be wifhed in the Report of the Academy ; but 

 it appears that the negative fparks from the conducSlor of Walckiers, which was tive feet 

 long, were from J 5 to 17 inches in length, very loud and denfe, and very painful to the 

 hand ; that pointed bodies emitted very fenfible fparks to the conduftor ; and that a battery 

 of 50 fquare feet was charged by 30 turns of the machine, which gives 19 feet of filk rub- 

 bed to charge one foot of glafs*. In another inftance, however, it is faid, that a fquare 

 foot was charged by one turn of the machine, which anfwered to 31 J^ fquare feet of filk. 

 It is not faid whether the labour of turning was confiderable or not. 



M. Rouland made feveral trials to fubftitute plain filk inftead of that which was var- 

 nlflied ; and he a!fo tried woollens and mixed cloth containing goat's hair; but none of 

 thefe anfwered to his fatisfa£lion. 



XII. 



Experimental Refearches concerning the Principle of the lateral Communication of Motion in Fluids,, 

 applied to the Explanati$n of various Hydraulic Phenomena, By Citizen J. B. VenTURI^ 

 Profeffor of Experimental Philofophy at Medena, Member of the Italian Society, of the InJU-^ 

 tUte of Bologna, the Agrarian Society of Turin, isfc. 



(Continued froTn page 276, vol, ii.) 



TPropofttion VI. 

 H E expence of fluid is lefs through cylindrical tubes than through conical tubes,, 

 which diverge from the commencement of the contrafted vein, and have the fame external 



diameter. 



• See Philof. Joura, I. 87. 



