116 Answer to Dr. Hare's Letter. 



I cannot conceive how in these cases the air in the vicinity of 

 the coating could gradually relinquish to it a portion of free elec- 

 tricity conveyed into it by what I call convection, since in the 

 first experiment quoted (1237), when the return was gradual, 

 there was no coating ; and in the second (1246) when there was 

 a coatings the return action was most sudden and instantaneous. 



xxix. Par. 4 of page 6, and par. 1 of page 7, perhaps only re- 

 quire a few words of explanation. In a charged Leyden jar, I 

 have considered the two opposite forces in the inductric and in- 

 ducteous surfaces, as being directed towards each other through 

 the glass of the jar, provided the jar have no projection of its 

 inner coating and is uninsulated on the outside, (1682.) When 

 discharged by a wire, or discharger, or any other of the many 

 arrangements used for that purpose, is made, these supply the 

 "some other directions" spoken of, (1682, 1683.) 



XXX. The inquiry in par. 2 of page 7, I should answer, by say- 

 ing, that the process is the same as that by which the polarity of 

 the sphere B, (iv, v,) would be neutralized, if the spheres A and 

 C were made to communicate by a metallic wire ; or that by 

 which the 100 or 1000 intermediate spheres (x), or the myriads 

 of polarized conducting particles (xi), would be discharged, if the 

 inner sphere A and the outer one C were brought into communi- 

 cation by an insulated wire ; a circumstance which would not 

 in the least affect the condition of the power on the exterior of 

 the globe C. 



xxxi. The obscurity in my papers which has led to your re- 

 marks in par. 1, page 8, arises, as it appears to me, (after my own 

 imperfect expression,) from the uncertain or double meaning of 

 the word discharge. You say, " if discharge involves a return 

 to the same state in vitreous particles, the same must be true in 

 those of the metallic wire ; wherefore then are these dissipated 

 when the discharge is sufficiently powerful ?" A jar is said to 

 be discharged when its charged state is reduced by any means, 

 and it is found in its first indifferent condition ; the word is then 

 used simply to express the state of the apparatus, and so I have 

 used it in the expressions criticised in par. 4 of page 6 already 

 referred to. The process of discharge, or the mode by which 

 the jar is brought into the discharged state, may be subdivided 

 as of various kinds; audi have spoken of conductive (1320), 

 electrolytic (1343), disruptive (1359), and convective (1562) dis- 



