170 Trans. Acad. Sci. of St. Louis. 
placed a sheet of glass and three layers of asbestos 
paper. 
The shield was mounted upon a heavy piece of timber 
and rested directly upon a sheet of glass. It was also 
wrapped with asbestos paper. The long suspension tube 
was held in stable position by three heavy silk cords at- 
tached to surrounding cases, and loaded with a series of 
distributed masses, about 25 in number, and having a 
mass varying from 50 to 100 grams each. The metal 
shield was loaded with two ten-pound masses of iron 
and its sides were clamped with wooden clamps in order 
to quiet any vibrations in the shield. The large iron 
masses and the metal shield were connected with each 
other by large copper wires, leading to a spark-knob 
mounted upon the table. Another spark-knob, mounted 
on an independent support, was provided with a dis- 
charge terminal, consisting of 150 pin-points, the heads 
of which were soldered to a copper disc. The entire ap- 
paratus was mounted upon a massive table. The floor 
of the room was of reinforced concrete. The discharge 
terminal was connected with the influence machine in an 
adjoining room, by means of brass rods hung upon silk 
cords. The machine was operated by a synchronous elec- 
tric motor. The discharge knobs at the machine were 
Separated so that no disruptive discharges were possible. 
One terminal of the machine was grounded. There were 
no condensers on the machine terminals. 
The time interval of a to and fro vibration of the sus- 
pended masses was 485 seconds. When at rest there 
appeared to be no disturbance of any kind. The reading 
would somtimes remain constant for hours. At other 
times the reading slowly changed. It often varied 
throughout a day through 20 scale divisions. It was 
found that the large masses appeared to attract the sus- 
pended masses with a varying force, even when the 
former were hung from the ceiling above. Sometimes they 
appeared to repel the suspended masses. These vary- 
ing effects were finally traced to very moderate changes 
