SCIENCE. 



[Vol. I., No. 4. 



that one of his students had shown that the 

 electrification of the air in the interior of a 

 laboratory could be readilj' perceived. Thom- 

 son then gave a short description of the kind 

 of room and the disposition of its walls which 

 would be desirable in an observatory for such 

 researches. The commission concluded to 

 recommend to the various governments regu- 

 lar obsei-vations on atmospheric electricity. 



An interesting discussion upon lightning- 

 rods then followed. Helmholtz said, that sta- 

 tistics in regard to strokes of lightning and in 

 regard to the effect of various kinds of light- 

 ning-rods were about to be collected in the 

 province of Schleswig-Holstein, the position of 

 this province between two seas being particu- 

 larly advantageous. It already had appeared 

 that the country is more exposed to strokes of 

 lightning than the cities, and that in villages 

 the public buildings were more frequently 

 struck than the houses. He also remarked, 

 that the academy of Berlin had recommended 

 the emplo3-ment on telephone-lines, where they 

 enter houses, of a lightning-protector, consist- 

 ing of two little spheres very near each other, 

 one of which is connected to the line, and the 

 other to the earth. M. Ludewig of German}' 

 gave some statistics in regard to damage to 

 telegraphic and telephonic apparatus in Ger- 

 many during the period from April 1, 1881, to 

 Aug. 20, 1881. During this time there had 

 been 2,301 storms ; and these had produced 

 2,165 cases of damage, more or less serious. 



It was debated whether a set of questions 

 in regard to the perturbing effect of storms 

 upon telegraphic apparatus should be issued. 

 After much discussion, a sub-committee was 

 formed to formulate a set of questions. Among 

 the members of this committee were Helm- 

 holtz and Mascart. The question of the ob- 

 servation of earth-currents was then taken up. 

 It was regretted that the existing telegraph- 

 lines running north and south, and east and 

 west, could not be utilized for the observation 

 of earth-currents. The pressure of business 

 usually prevented this. M. Blavier pointed 

 out, that the earth-currents are generally too 

 feeble to be observed on telegraph-lines which 



are in operation. Moreover, the polarization 

 of the earth-plates of the battery would cause 

 trouble. Mascart, in reply, said that he had 

 noticed that the maximum disturbance was 

 reached slowly, through a period of several 

 daj's, and died out also slowly. He therefore 

 thought that existing telegraphic lines could 

 be used, notwithstanding the objections of 

 M. Blavier. He proposed that observations 

 should be made upon lines reserved for the 

 purpose, and also on existing telegraphic sys- 

 tems. A question arose upon the length that 

 these lines should have. Helmholtz remarked, 

 that one could make observations on lines 

 from one to two kilonietres in length. It 

 would be necessary, however, to shun the 

 effects of polarization of the .electrodes. He 

 thought that special plates surrounded by per- 

 oxide of manganese might be serviceable. 



The commission in general were in accord 

 on the necessity of organizing a systematic 

 study of earth-currents upon telegraphic lines, 

 or at least records of these currents on the days 

 specified for observations by the international 

 polar expeditions (the first and fifteenth of e^ch 

 month, from September, 1882, to September, 

 1883). In a general discussion which fol- 

 lowed, upon lightning-conductors and electrical 

 storms, Helmholtz expressed his doubt about 

 the efficacy of extent of contact of lightning- 

 conductors with the earth, and the varied 

 nature of the plates emplo3'ed. M. Van der 

 Mensbrugghe (Belgium) spoke of the desira- 

 bility of studying the nature of lightning dis- 

 charges, especially that termed ball-lightning. 

 Mascart replied, that he did not believe that 

 cases of ball or globular lightning were well 

 substantiated. It might happen that it was an 

 illusion of the senses, and could therefore be 

 relegated to physiology rather than to phj'sics: 

 The commission then discussed the question 

 of studying the best conditions for the estab- 

 lishment of an international telemeteorographic 

 system, which would permit various stations in 

 different countries to communicate continuous- 

 ly with each other. They decided that it did 

 not appear that the time had come for the 

 establishment of such a system ; but they ex- 



