1Q2 PHILOSOPHICAL TRANSACTIONS. [aNNO 1751. 



its quantity) it is immediately and equally diffused through the whole. Thus 

 common matter is a kind of sponge to the electrical fluid ; and as a sponge would 

 receive no water, if the parts of water were not smaller than the pores of the 

 sponge ; and even then but slowly, if there was not a mutual attraction between 

 those parts and the parts of the sponge ; and would still imbibe it faster, if the 

 mutual attraction among the parts of the water did not impede, soiijg force being 

 required to separate them ; and fastest if, instead of attraction, there were a 

 mutual repulsion among those parts, which would act in conjunction with the 

 attraction of the sponge : so is the case between the electrical and common mat- 

 ter. In common matter indeed there is generally as much of the electrical as it 

 will contain within its substance : if more is added, it lies without upon the sur- 

 face,* and forms what we call an electrical atmosphere ; and then the body is 

 said to be electrified. 



It is supposed, that all kinds of common matter do not attract and retain the 

 electrical with equal force, for reasons to be given hereafter , and that those 

 called electrics per se, as glass, &c. attract and retain it the strongest, and con- 

 tain the greatest quantity. We know that the electrical fluid is in common 

 matter, because we can pump it out by the globe or tube ; and that common 

 matter has near as much as it can contain ; because, when we add a little more 

 to any portion of it, the additional quantity does not enter, but forms an elec- 

 trical atmosphere ; and we know that common matter has not generally more 

 than it can contain ; otherwise all loose portions of it would repel each other, as 

 they constantly do when they have electric atmospheres. 



The form of the electrical atmosphere is that of the body which it surrounds. 

 This shape may be rendered visible in a still air, by raising a smoke from dry 

 resin dropped into a hot tea-spoon under the electrized body, which will be at- 

 tracted and spread itself equally on all sides, covering and concealing the body. 

 And this form it takes, because it is attracted by all parts of the surface of the 

 body, though it cannot enter the substance already replete. Without this attrac- 

 tion it would not remain round the body, but be dissipated in the air. The 

 atmosphere of electrical particles surrounding an electrified sphere is not more 

 disposed to leave it, or more easily drawn off" from any one part of the sphere 

 than from another, because it is equally attracted by every part. But that is not 

 the case with bodies of any other figure. From a cube it is more easily drawn at 

 the comers than at the plane sides, and so from the angles of a body of any 

 other form, and still most easily from the angle that is most acute ; and for this 



* The author of this account is of opinion, that what is here added, lies not only without upon the 

 surface, but penetrates with the same degree of density the whole mass of common matter, upon 

 which it is directed. — Orig. 



