MR. W. CROOKES ON MOLECULAR PHYSICS IN HIGH VACUA. 647 
8 millims. from the negative pole, no movement of the gold leaves takes place whether 
a or b is negative, and whether c is connected with earth or is insulated. 
At a good exhaustion, when the green phosphorescence of the glass is strong, the 
gold leaves are only slightly affected whichever way the current passes. 
598. On increasing the exhaustion to a very high point, so that the green phospho¬ 
rescence gets weaker and the spark has a difficulty in passing, the gold leaves are 
violently affected. When the pole a is negative and b positive, the leaves diverge to 
their fullest extent. On examining their potential it is found to be positive. The 
coil was stopped and the gold leaves remained open. A touch with the finger caused 
them to collapse. They then gradually opened again, but not to the original extent. 
The finger again discharged them, when they reopened slightly a third time. Experi¬ 
ment showed that the electrical excitement took many minutes to recover equilibrium. 
A Leyden jar put to the idle pole d was charged positively. 
599. The earth wire and electroscope remaining as shown in the figure, the direction 
of current was reversed, so as to make a positive and b negative. The gold leaves 
were now less strongly affected; they opened a little, and remained quivering, as if 
under the influence of rapidly-alternating currents. 
Eio-. 8. 
600. The wires were rearranged as shown in fig. 8, b and d being connected with 
the coil. When d was made negative faint sparks about 1 millim. long could be 
drawn by the finger from c ; but when d was made positive the sparks from c were 
10 millims. long. The same results are obtained when the finger is brought near a, so 
long as c remains insulated. If, however, c be connected with earth by a wire, no 
sparks can be got from a, whichever way the current passes between b and d. Con¬ 
necting a with earth diminishes the length of the sparks which can be drawn from c 
by about one-half. 
The poles a and b being connected with the coil, and the idle poles c and d having 
loose wires hanging from them, the wires were strongly repelled from each other. 
601. The above experiments show that an idle pole in the direct line between the 
positive and the negative poles, and consequently receiving the full impact of the 
molecules driven from the negative pole, has a strong positive charge. 
602. It now became of interest to ascertain whether the trajectory of the molecules 
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