334 PHILOSOPHICAL TRANSACTIONS. [aNNO )75g. 



XII I. Electrical Experiments and Observatioris. By Edward Delaval, M. A. 



p. 83. 



Mr. D. filled several small glass tubes with the dry powders of calcined me- 

 tals, viz. ceruss, lead ashes, minium, calx of antimony, &c. Into each end of 

 every tube he put a piece of iron wire, which communicated with the calx, and 

 fastened them with wax : so that the electric fluid, not being able to escape 

 by means of the glass, must either pass through the calx, or not at all. On 

 hanging one of the wires, bent for the purpose, to the electrified bar, and 

 holding the other in his hand, he observed that no electric matter passed the 

 calx, the snaps issuing all the while from the bar, or from that wire which was 

 in contact with the bar. Animal and vegetable solids also, when reduced to 

 ashes, and interposed in the same manner between two pieces of wire, he found 

 as eflfectually intercept the electric stream, as the metallic calces. From these 

 experiments we see, that animal, vegetable, and metallic bodies, though such 

 known conductors of the electric fluid while in their entire state, are easily 

 changed into resisters, or non-conductors of it. 



Mr. D. was led to attempt this change from its having been observed, that 

 dry mould would not conduct the electric fluid ; and thence he suspected, 

 that one class of the non-conductors must owe its property to an electrical virtue 

 that would be found to reside in the calx, or earth of the chymists, after it is 

 divested of the unctuous inflammable matter, which constitutes another of the 

 chymical principles called sulphur ; in like manner as this sulphur is constantly 

 found highly electrical in all bodies where it abounds in a solid form, viz. resins, 

 wax, &c. It must be remembered, that there is a remarkable and well-known 

 opposition to the electrical effects of these two classes ; the earthy one (as glass 

 and stones) electrifying plus, and the sulphureous one minus. Does it not 

 seem then a thing to be expected, in a body compounded of both, that the op- 

 posite powers of these ingredients should counterbalance and destroy the effects 

 of each other, and the body in which the positive and negative ones equally 

 prevail, become neutral, or non-electric? 



There is another process, natural and without fire, which is supposed to de- 

 stroy the sulphureous substance of metals, viz. when they are corroded, and 

 moulder in the open air. Accordingly, with the same apparatus in which I 

 tried the calcinations by fire, I examined the common rust of iron, and flake- 

 white, which is the rust of lead, and find them equally converted into non-con- 

 ductors in the open air. That this change, in metals particularly, is not owing 

 to, or promoted by, the circumstance of mere pulverization, is evident, not 

 only because the above-mentioned calces are equally strong electrics when 

 formed into hard masses with a thin paste of flour and water, and after- 



