38 



I. GUARESCHI 



froin the other parts of the inner surface of the suirounding chamber, and equal to the amount 

 of force existed in ali directions by A. I need net refer partieularly to irregular and mixed 

 cases, as the walls of a room (1434) or more complicated results (1337, 1566, 1679, etc.) : the 

 principles are the sanie and the amount of action always definite. 



If another conductor, either insulated or connected with the earth, be approached to the 

 former conductor, then lines of induction force are transferred to it from the former induction 

 bodies (1225, 1449). Thus, if F be such a body, then electric force or lines, which before pro- 

 ceeded towards B or towards H, are transferred to F; and if F be insulated, with the sanie 

 development of contrary force as before. If F be iminsulated and large, the part behind it, at H, 

 may even receive no charge , but be in the naturai state : and the sum of power upon the 

 inner surface of the envellope H, D, E will be less than the sum of contrary power on A, by 

 so much as is disposed of on the surface of an uninsulated F. 



I know no distinction between free and dissimulateci electricity (1684). Both are cases of 

 induction and change by induction. If the electricity between A and E is not dissimulated, 

 neither is that between A and B, or between A and F. It might as well be said that the 

 lightning which falls upon and kills a man is free to him, but is dissimulated to one who is 

 a few miles distant: the difference is merely one of circumstance not of principle. Whether 

 the inductric body induces upon me or upon another person, raakes no diiference in the action 



If the sum of power be 20, as much as 15 may be towards me and only 5 to him: but 

 the land of action is alike in both cases and the sum of the power remains the same. 



Ali charge is induction: ali induction is charge (1177, 1178, 130, 1682). A short but im- 

 perfect summary is contained in the paragraphs from 1667 to 1684. You will find also in 



Fig. 4. Fig. 6. Fig. 6. 



the Philosophical Magazine, 1843, voi. XXII, p. 200, in voi. II of the 8"' Edition of my Expe- 

 rimental ReseaVches, p. 279, some demonstrative experiments on static induction. I bave been 

 accustomed for years past, to shew very many forms of experiments founded on these prin- 

 ciples ; I will describe one which seems to embrace many of the results you describe to me. 

 A conductor A is sustained in a charged state by connexion with a (fig. 4) Leyden-jar : an 

 insulated brass piate is brought near it, and then the surfaces examined by a Coulombs proof 

 piane or carrier (which I hold to be unexceptionable when properly employed) and the sur- 

 face of 6 seems to be contrary to A (fig. 5), whilst the surface of c is like that of a. The two plates 

 close together and connected (fig. 6), replace the one- piate a the surfaces b and c found like the 

 former surfaces. Then the plates are opened about an inch being stili connected by a brass 

 rod on (fig. 7 ) which they bang, b and c are found as before ; but within at d there is no electri- 

 city of either kind on either surface. 



Ali the time there is electricity like that of A to be found at the edges of the plates, 

 provided irregular Jateral inductions be prevented. Then the plates are more opened out, stili the 

 electricity at (fig. 8) b and c is the same, but that at the edges of the near piate b, begins to 

 lose its A character and eithèr be neutral or assume that of b. Being more opened out, the 

 electricity of b creeps round the edge of the piate (fig. 9), approaching nearer to the middle at 

 the piate b is smaller, or the sign of A larger, or its power more intense; and the electricity of c 

 also becomes more extended over the surface a round the edges of that piate, according to its 

 size and position in relation to surrounding bodies. If an uninsulated conductor be brought 

 towards any part of the compound system of plates a rod, as at 1, 2, 3, 4, it immediately 

 renders these places electric like A, either causing or exalting their state, whilst it acquires 

 through the induction, a state the contrary of A or like that of b. If exited shell lac be 



