﻿22 EQUIPMENT AND WORK OF AX AERO-PHYSICAL OBSERVATORY. 



J. J. Thomson (see " Xature," July 26, 1894) holds that a molecule of 

 gas cannot be electrified, but that the atoms may be. The question as 

 it presents itself to his mind is. "" Is the electricity in the charged gas 

 carried by molecules or atoms? "' "A square centimetre of surface im- 

 mersed in air at standard temperature and pressure is struck b}' about 

 10" molecules per second, yet such a surface will retain for hours with- 

 out sensible loss a charge of electricity which, as we know from the 

 electrolytic properties of liquids and gases, could be carried by a few 

 thousand million of particles if these were to receive such a charge as 

 the atoms of the air are able to carry." 



We see, then, how much remains to be determined and how valuable 

 in connection with the jiroposed electrometric survey the aero-physical 

 laborator}^ would be. 



Returning now to the results'of Elster and Geitel, under their fourth 

 deduction it is said that the morning maximum in the potential curve 

 was not observed at a height of 10,168 feet. This, we think, is a most 

 interesting result, and the result should be confirmed or disproved with- 

 out delay. If need be, observations of the potential at great heights could 

 be made by the aid of kites. With regard to the fifth result, the positive 

 fall of potential within a cloud which gave but a small quantity of rain, 

 we can only say that the whole subject of the relation of potential to 

 rainfall calls for investigation. Much has been surmised and but little 

 done. Our experimental evidence is scanty, being limited to a stray 

 observation here and there. One interesting observation made on Au- 

 gust 9, 1892. may be referred to. A kite connected by wire with a 

 quadrant electrometer was raised and kept at some elevation above the 

 summit of Blue hill, Massachusetts. At 7.40 p. m. a thunderstorm, 

 which for some twenty minutes had been approaching from the west, 

 was near enough to cause an incessant stream of sparks from the kite 

 string. When the string was connected over a Mascaii; insulator to 

 the electrometer — i. e., the needle, one set of quadrants being charged 

 highlv positive and the other highly negative — a sizzling discharge oc- 

 curred. Stinging shocks could be felt on touching the kite wire, and if 

 a ground wire near by was held within a fraction of an inch a discharge 

 of sparks ensued. Rain began about 8.10 p. m. and ended in a few min- 

 utes, the amount being about one-hundredth of an inch ; lightning was 

 frequent and vivid to the north and northeast, and, as we learned the 

 next day, did much damage to barns in that localit.y. Although the 

 electrical phenomena were to be seen thus plainly from ten to fifteen 

 miles aw^a}", we were not able after the rain to obtain sparks from the 

 kite wire. This seems therefore to confirm the Sonnblick observation. 



With regard to Saint Elmo's fire, it is of interest to quote in conjunction 

 with the Sonnblick experiments the Ben Xevis observations. Buchan 



