C. GENERAL PHYSICS. 171 



of the potential of liquid surfaces, is led to a conclusion of 

 capital importance to meteorology. His equations, namely, 

 seem to prove rigorously that any change in the surface of 

 the liquid gives rise to a change of temperature, and, if the 

 circuit is closed, to a thermo-electric current. His experi- 

 ments show that, on the one hand, the water of the ocean 

 under the action of the sun, being submitted to a continual 

 evaporation, must afiect the calorific and the electric state of 

 the earth, and develop constant thermo-electric currents. 

 On the other hand, the enormous quantity of vapor which is 

 lifted into the atmosphere is there subjected to incessant 

 variations in respect to the surfaces of contact with the air 

 of its vesicles, raindrops, etc. Its reduction from a state of 

 extreme and almost molecular tenuity to a state where, by 

 sudden condensation it forms larger raindrops, enables it to 

 actually produce enormous quantities of electricity, until the 

 drops fall in turn upon the surface of the globe from which 

 they were elevated. Thus Ave have at once, on the one 

 hand, the existence of a constant source of thermo-electricity 

 circulating around the earth, and on the other hand a per- 

 manent cause of atmospheric electricity. Bulletin Acad. 

 Hoyal des Sciences de Belgique^ Bruxelles^ 1876, 782. 



LIGHTNING FROX A CLEAR SKY. 



The rare phenomenon of a stroke of lightning from a clear 

 sky was observed on the 3d of July, at 4 P.M., at Senften- 

 burg. Saxony. At that time a thunder-storm was observed 

 so far. distant that some thirteen to fifteen seconds elapsed 

 between the flashes and the thunder, when suddenly in the 

 clear sky, in the immediate neighborhood of the observer. 

 Dr. Roch, a blinding flash and fearful thunder occurred. 

 Especially noteworthy was it that this abnormal flash put an 

 end to all the distant lightning and thunder; and the storm 

 clouds very quickly disappeared from the heavens, which re- 

 tained during the night their original purity. Sitzb. Naturw. 

 Gesells. ^^Isis,'^ Dresden, December, 1875, 118. 



PROTECTION AGAINST LIGHTNING STROKES. 



In his annual address as President of the Meteorological 

 Society, Dr. R. J. Mann states that Professor Melsens, of 

 Brussels, has been for some time engaged in an interesting 



