170 Mr. Charles Tomlinson on 



but not in sufficient number to form a sect ; and also indiffer- 

 entists, who say that the two former classes quarrel about what 

 no one understands. Thus Kamtz refers to hail as a phenomenon 

 " welches sehr h'aufig Begleiter der Gewitter ist, und dessen 

 Erklarung sehr schwierig ist." Nevertheless his elaborate 

 treatment of this subject is included in the chapter on Atmo- 

 spheric Electricity l . Pouillet more emphatically declares : — 

 " On ne sait rien jusqu'a present sur les causes qui determinent 

 ce phenomene" 2 . Becquerel also confirms the remark : — 

 " Nous ignorons encore quelle est la veritable origine de ce 

 phenomene"" 3 . 



Yet there is something very enticing in the electrical theory 

 of hail. Hail often accompanies the thunderstorm ; and the 

 stones, in falling, have been known to flash with electric light 4 . 

 It is true that in the last century, when Franklin's experiments 

 were exciting delight and enquiry in various parts of Europe, 

 more burdens were laid on electricity than it was well able to 

 bear ; and we may perhaps allow a good-natured smile to pass 

 in reading Father Beccaria's statement that " a more intense 

 electricity unites the particles of hail more closely than the 

 more moderate electricity does those of snow" 5 . M. de 

 Morveau also supposes that, evaporation being the immediate 

 cause of the cooling, and electricity augmenting perceptibly 

 the evaporation, " le fluide electrique est une cause habituelle 

 plus ou moins immediate de la formation de la grele" 6 . 



Without referring further to the ideas of the older physicists 

 as to the formation of hail, I pass on to a meteorologist nearer 

 our own time, who exerted considerable influence on the science 

 of meteorology — if such it can even now be called. Professor 

 Daniell 7 admits the difficulty of accounting for the phenomena 

 of hail on account of our imperfect knowledge of the influence 

 of electricity. As a proof of electrical action, he calls attention 

 to the behaviour of the electrometer on the approach of hail, 

 when the electricity will not only be found frequently to change 

 in intensity, but also to pass from positive to negative, and 

 vice versa, ten or twelve times in a minute. 



From this action on the electrometer Kamtz was led to 

 include hail under atmospheric electricity. Even the small 

 hail that falls in winter (which the Germans name Graupel, and 



1 Lehrbuch der Meteorologie, ii. p. 495. 



2 Elemens de Physique et de Meteorologie. 



3 Traite de VEleetricite, iv. p. 151. 



4 Luke Howard, ' Climate of London,' cites examples of luminous hail. 



5 Quoted in Priestley's ' History of Electricity.' 



6 Bertholon, De VElectricite des Meteores, ii. p. 189. This was at one 

 time a work of considerable authority. 



7 Elements of Meteorology, 3rd edition, 1845, i. p. 241. 



