4C0 PROCEEDINGS OF THE AMERICAN ACADEMY 



twine, previously soaked in a mixture of glycerine and water. The 

 end of this string was connected to a wire well insulated, which in 

 turn was connected to one set of the quadrants of the Trowbridge 

 electrometer, the other set of quadrants being connected with the 

 ground. The needle was connected to the positive pole of a Beetz 

 solid battery of 200 cells (200 volts). The needle was at once de- 

 flected to its limit, indicating a high positive potential for the air at- 

 an elevation of less than 300 feet. Remaining for a few seconds 

 at this high positive, it would suddenly change to an equally high 

 negative, sometimes without the least warning. It was, without doubt, 

 extremely variable. The high positive indications seemed to be more 

 prevalent. Connecting the kite-string with the multiple quadrant 

 electrometer, described in this paper, the following results were 

 obtained. The connection and charge of the needle were as in the 

 other instrument. A fine index-pointer records the deflections in this 

 instrument, and the mirror, scale, and dark room are dispensed with. 

 A Danicll cell gives a deflection of half a degree. The deflection 

 given by the kite was at times over 25 degrees in a positive direction, 

 or equivalent to over 100 volts. The index-hand was seldom still, 

 as in the previous case evidencing an extreme variableness of the 

 electrical condition of the air at that place and time. The wind was 

 from the east, steady and light, the pressure 30.0G1, the temperature 

 49° F., the relative humidity 77, and the sky covered with a low 

 pallium of stratus clouds moving from the east slowly. 



On the next day. May 7, the kite was again flown, this time reach- 

 ing an altitude of about 500 feet. The potential of the air at a point 

 ten feet from the ground, obtained by a water-dropper, reduced to 

 volts, was 0.4. 



The table on the following page shows the deflections for short in- 

 tervals. These deflections were comparatively steady, and had not the 

 variableness of those on the preceding day. The wind was east, and 

 had now been blowing from that quarter for nearly thirty hours. The 

 sky was covered with stratus clouds, having the unusual appearance of 

 billows with the crests pointing to the earth. The pressure was 30.040, 

 the temperature 45° F., the relative humidity 75. 



The experiment demonstrates that it is comparatively easy to 

 obtain some indication, even if it be only a relativ'e one, of the 

 potential of the air at hiirh altitudes. The method is simple and 

 direct, and with the exception of the original cost of electrometer and 

 charging battery, quite inexpensive. A series of simultaneous obser- 

 vations of this character would doubtless be of value in meteorology. 



