742 POPULAR SCIENCE MONTHLY. 



lently deflected and large sparks obtained at other times. Day 

 after day as we flew the kite we found this high electrification of 

 the air, and we had no trouble in getting sparks even when the 

 sky was cloudless. One other discovery was made, and this would 

 have delighted Franklin more than the other, for he was always 

 most pleased when a practical application was in sight. Seated 

 within the instrument room of the observatory, with his back to 

 the open window through which came the kite wire carefully 



MASCART ELECTROMETER, WITH PHOTOGRAPHIC REGISTER, JULY, 1892. 

 Blue Hill Meteorological Observatory. 



insulated, and the kite high in air, the observer closely watching 

 the index of the electrometer could tell positively, and as quickly 

 as one outside watching the kite, whether it rose or fell. When 

 the kite rose, up went the voltage, and vice versa. In other 

 words, the electric potential of the air increased with elevation. 

 It must be confessed that the kites made to- day would have be- 

 haved better and flown with more steadiness than the one we 

 used. It may have been the varying wind, or more likely wrong 

 proportions in the kite and tail; but our old hexagonal kite 



