6 Introduction 



blunt conductors ; but the other four members of the Committee, Messrs 

 Cavendish, Franklin, Watson, and Robertson, having heard and con- 

 sidered these objections, found no reason to change their opinion or vary 

 from their Report*. 



But on the isth May 1777, the Board House at Purfleet was struck 

 by lightning, and some of the brickwork damaged. This being communi- 

 cated by the Board of Ordnance to the Royal Society f, a Committee was 

 appointed to examine the effects of the lightning and to report. 



The Committee consisted of Mr Henly, Mr Lane, Mr Nairne and Mr 

 Planta, Secretary of the Royal Society. They reported in favour of making 

 a channel all round the parapet and filling it with lead, and connecting 

 this in four places with the main conductor on the roof of the building. 



Mr Wilson, however, dissented from this Report, and communicated 

 to the Royal Society an account of a most elaborate and indeed mag- 

 nificent set of experiments conducted in the Pantheon, in which a cylinder 

 155 feet long, composed of 120 drums, and connected with a wire 4800 feet 

 long, suspended on silk strings, was electrified, and the discharge made 

 to strike a model of the Board House at Purfleet. The experiments were 

 witnessed by King George III, and seem to have been very brilliant. The 

 picture of the experiment, probably drawn by Mr Wilson, is, as a work 

 of art, considerably above the average of the plates in the Philosophical 

 Transactions. 



The subject was referred to a larger Committee, consisting of Sir John 

 Pringle, President of the Royal Society, Dr Watson, Henry Cavendish, 

 W. Henly, Bishop Horsley, T. Lane, Lord Mahon, Edw. Nairne, and 

 Dr Priestley. 



They reported! in favour of having an additional number of con- 

 ductors ten feet high, terminated with pieces of copper eighteen inches 

 long, and as finely tapered and acutely pointed as possible. 



We give these directions (they conclude), being persuaded, that elevated 

 rods are preferable to low conductors terminated in rounded ends, knobs, or 

 balls of metal; and conceiving, that the experiments and reasons made and 

 alledged to the contrary by Mr Wilson, are inconclusive. 



I have stated this incident at some length because it does not appear 

 to have been noticed by Cavendish's biographers, and because it shows 

 him cooperating with Franklin and others in an electrical investigation 

 undertaken in the interest of the nation. 



Cavendish's researches on the electric current have been hitherto very 

 imperfectly known, as they are only alluded to in his celebrated paper on 

 the Torpedo. The private investigations of Cavendish are contained in 

 this volume, but the external events which were more or less connected 

 with them, were as follows: 



Phil. Trans. 1772, p. 66. f Ib - J 77 8 . P- 2 3 2 - t Ib - P- 3*3- 



