272 APPENDIX 



and seven in the morning in summer, and between ten and 

 twelve in winter ; the minimum comes between five and six 

 in the afternoon in summer, and about three in the after- 

 noon in winter. There is a second maximum at sunset, 

 followed by a diminution during the night until sunrise. 

 (Flammarion, 1905.) 



Fulminic matter, remarks the same author, is strongly 

 attracted towards damp regions, and is guided on its way 

 to the earth by the hygrometrical conditions of the atmo- 

 sphere. Violet lightning is thought to come from the 

 upper stratum of the atmosphere, and a flash has been 

 found to have a maximum length, as observed from the 

 earth, of over eleven miles. 



That earth-currents have, at times, an origin which is 

 in part thermal seems not unlikely. Earthquakes are of 

 common occurrence in the tropics, and I remember two 

 on the East Coast of Africa. One made a difference of 

 750 fathoms in the soundings off Mozambique, and the 

 other was experienced at Delagoa Bay much about the 

 time that the earth-current rose to forty volts. It is a 

 curious fact, though probably only a coincidence, that the 

 submarine upheaval off Mozambique, the earthquake at 

 Delagoa Bay, and the forty-volt earth-current before 

 mentioned took the same course, i.e., north and south. 

 Dutton records an instance of an earthquake at the 

 Yaqui river which disturbed the needle of the magneto- 

 graph at Los Angeles, a distance of more than six hundred 

 miles, and it is possible that forces which in themselves 

 are insufficient to cause even a slight convulsion of Nature 

 may be responsible for the creation of high potential at one 

 point, whence it is distributed to another point or points of 

 lower potential ; the precise path being governed by electro, 

 lytes in the earth, or, in other words, by the same law which 

 directs the course of lightning through the atmosphere. 



In speaking of earthquakes we must, of course, 



