On the Electricity of Mercury -falls. 903 



molecules unit distance apart. Now the gravitational 

 attraction obeys the inverse square law, and its va]ue for two 

 ether molecules separated by unit distance should therefore 

 be equal to the above value of K. The former quantity is equal 

 to 1*84 x 10" 52 dyne, which is much smaller than the latter; 

 and this law cannot therefore account for the latent heat of eva- 

 poration. Apart from molecular attraction considerations the 

 latent heat formula given by Mills is, however, of great interest. 



To be on safe ground the law deduced from latent heat 

 data must contain an arbitrary function. But still the law 

 may give some valuable information, for we might be able to 

 prove that the arbitrary function cannot include some of the 

 known parts of the law obtained, and these parts may bring- 

 out some important properties, and these must be true. 



Yours faithfully, 



Cambridge, Oct. 5, 1910. R. KLEEMAN. 



CI. Note on the Electricity of Mercury-falls and on very 

 large Ions. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, — 



REFERRING to the paper by Mr. Lonsdale in your 

 September number, on the "Ionization produced by 

 the Splashing of Mercury," I may perhaps mention to your 

 readers, that Mr. Lonsdale's results, which are certainly of 

 great interest, are, however, not so new as may seem. Most 

 of these results, including the large excess of the one kind 

 of carriers (ions), the small velocity of these carriers, the 

 influence of the surface of impact, are to be found in two 

 elaborate papers by A. Becker, published in the Annalen der 

 Physik, vol. xxix. p. 909, in 1909, and vol. xxxi. p. 98, in 1910, 

 " Ueber Quecksilberfall elektricitat" ("On the Electricity 

 of Mercury-falls"). Prof. Becker shows there also, that the 

 smallest impurities of the mercury are of great influence, and he 

 comes to employ very-carefully purified mercury. Moreover, 

 in the same papers there are also to be found experiments with 

 several amalgams and in other gases than air (H 2 , C0 2 ), and 

 the surface of impact is also further varied. 



As to the last point in Mr. Lonsdale's summary of results, 

 viz. the appearance of " neutral doublets," reference may be 

 made to the paper by K. Kahler (Ann. d. Phys. vol. xii. 

 1903), who found quite the same appearance of new carriers 

 of electricity in the air from waterfalls which had already 

 passed an electric field and was therefore expected to be free 

 from carriers. According to the state of knowledge at that 

 time, Mr. Kahler interpreted his result as "radioactive 



