340 PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



reserved for a different purpose. The several ends of those 4 parts were closed 

 up with board, rounded off at the edges in every part, and covered with tin-foil 

 likewise. 



This great cylinder, consisting of the 3 parts, was suspended about 5 or 6 

 feet from the floor by silk, lines; and formed a curve in the room, something 

 like a horse-shoe; one end of which hung over the middle of the long frame, 

 on which the model was proposed to move; the other, which I call the further 

 end, was joined occasionally to the end of a long wire, that was suspended 

 through the whole space of the room. And lest the several atmospheres round 

 this wire, in its charged state, might, in consequence of the unavoidable returns 

 of the wire, interfere too much with each other, it was suspended in such a 

 manner, by silk lines also, that each length was 5 or 6 feet from its neighbour: 

 and those that were suspended nearest to the great cylinder hung at the same 

 distance from it. The remote end of this long wire hooked on occasionally at 

 the end of the brass drums, which made a separate cylinder (the 4th part alluded 

 to above) about 10 feet in length: this was suspended likewise by silk lines, and 

 about 6 feet from the floor; but in such a manner, that the furthest end of it 

 from the wire was within 9 or 10 feet of the great cylinder. The long wire, 

 with the great cylinder and brass drums, made the whole of the substitute for a 

 thunder-cloud, when they were properly charged. 



The machine, employed to charge this apparatus, consisted at first of 2 large 

 glass cylinders turned by one wheel. But as the friction arising from the '2 

 together rendered it difficult to work them, and the advantage gained from both 

 in the charge itself was found to be not so considerable as might reasonably be 

 expected, one of them only was made use of in the following experiments. 

 The place where this machine charged the great cylinder, was about 10 or 11 

 feet from its nearest end. It was found expedient to be provided also with 

 another machine; but this was employed only on particular occasions, and was 

 generally placed at the further end of the great cylinder. 



The floor of the room being of baked wood, it was necessary to have wires 

 properly connected with the cushions of both machines along the floor, where 

 they were joined to another wire, which communicated with the well, in 

 order to conduct the fluid more readily than the baked wood admitted of. The 

 whole of this apparatus, so contrived, was disposed in the great room of the 

 Pantheon, by the favour of the proprietors, who, having heard that a large 

 apartment was wanted, in which to show before the Board of Ordnance and the 

 R. s. these experiments, were pleased to honour me with a very polite letter, 

 offering the use of that elegant building for the purposes intended. 



Exp. 1 . The model, with a pointed conductor on it (which, in a ilegree of 

 sharpness, was nearly equal to that of a common darning needle) being placed 



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