His work unknown to his contemporaries 1 5 



experiments made in October, 1772. Cavendish appears, however, to have 

 got wrong in his reckoning for a good many days together during that 

 month. See Art. 502. 



It is somewhat difficult to account for the fact, that though Cavendish 

 had prepared a complete description of his experiments on the charges 

 of bodies, and had even taken the trouble to write out a fair copy, and 

 though all this seems to have been done before 1774, and he continued to 

 make experiments in electricity till 1781, and lived on till 1810, he kept 

 his manuscript by him and never published it. It was not till 1784 that 

 he communicated to the Royal Society those "Experiments on Air," in- 

 cluding the production of water and of nitric acid, the absorbing interest 

 of which might perhaps account for some neglect of his electrical writings. 



Cavendish cared more for investigation than for publication. He would 

 undertake the most laborious researches in order to clear up a difficulty 

 which no one but himself could appreciate, or was even aware of, and we 

 cannot doubt that the result of his enquiries, when successful, gave him a 

 certain degree of satisfaction. But it did not excite in him that desire to 

 communicate the discovery to others which, in the case of ordinary men 

 of science, generally ensures the publication of their results. How com- 

 pletely these researches of Cavendish remained unknown to other men of 

 science is shown by the external history of electricity. 



Viscount Mahon, afterwards Lord Stanhope, a man of great ingenuity 

 and fertility in invention, a pupil of Le Sage of Geneva, and the inventor 

 of the printing press which bears his name, published in 1779 his Principles 

 of Electricity. The theory developed in this book is that 



A positively electrified body surrounded by air will deposit upon all the 

 particles of that Air which shall come successively into contact with it, a pro- 

 portional part of its superabundant Electricity, By which means, the Air sur- 

 rounding that body will also become positively electrified : that is to say, it will 

 form round that positive body, an electrical atmosphere, which will likewise 

 be positive, (p. 7.) 



That the electrical Density of all such Atmospheres decreases, when the 

 distance from the charged Body is increased, (p. 14.) 



He then proceeds to determine the law of the density of the electrical 

 atmosphere, as it depends on the distance from the charged body. He 

 assumes that if a cylinder with hemispherical ends is placed in the electrical 

 atmosphere of a charged body, the density of the electricity at any part 

 of the cylinder will depend on the density of the electrical atmosphere in 

 contact with it. 



He also shows by experiment that if the cylinder is insulated, and 

 originally without charge, it does not become charged as a whole by being 

 immersed in the electrical atmosphere of a charged body. Hence, when 

 the electricity of the cylinder is disturbed, the whole positive charge on 





