NEW EVIDENCE OF A RELATION BETWEEN 
GRAVITATION AND ELECTRICAL ACTION, 
AND OF LOCAL CHANGES IN THE ELEC- 
TRICAL POTENTIAL OF THE EARTH.* 
Francis KH. NipHer, 
In the work to be here described, the apparatus used 
was a modified form of that used by Cavendish, as shown 
in the former paper, published by the Academy of Science 
of St. Louis, Vol. XXIII, pp. 183-4-5. 
The wood frame was in this case covered with tin-foil, 
within and without. The sheet metal forming the sides of 
the shield were clamped to the wood frame, by bars of 
wood which were also covered with tin-foil. All joints 
were sealed with wax before the tin-foil was put in place. 
The whole shield was then surrounded by two end caps 
of metal which meet at the middle of the shield and are 
sealed together by means of tin-foil. A layer of air was 
thus formed between the two metal shields surrounding 
the suspended masses. Hither of these two metal shields 
was considered ample protection to prevent the sus- 
pended masses from being acted upon electrically by the 
large masses. The layer of air between the two shields 
was designed to diminish convection effects within the 
shield due to changes in the temperature of the room, 
and changes in the temperature of the air within the 
room were made as small as possible, by cutting off all 
sources of artificial heat. It did not usually vary more 
than 1.5 degrees C. during the day. The temperature 
was determined by means of a thermometer placed near 
the large masses. The reading was by means of a tele- 
scope. The reading could be made accurately to tenths 
of a degree C. and hundredths of a degree could be esti- 
mated with fair precision. The air within the shield was 
(383) 
