160 Intelligence and Miscellaneous Articles. 
repeated discharging, resumes almost equal intensity. Only after 
the lapse of some hours does the pile get back to its initial 
condition. 
For experiments of this kind a form of the pile is adapted 
which is also in other respects to be recommended for the purpose 
of demonstration : the pairs of plates are strung, by means of a 
needle, upon a strong silk thread. In this form it can be easily 
placed between the dischargers of the machine, and disturbing 
influences, such as appear when a glass envelopment is employed, 
are avoided. A pile of ] 1,000 pairs of plates of 1 square centim. 
surface, after ten minutes' charging, gave sparks of about 1 millim. 
length, between two metal balls connected with the poles, and 
rendered a small Geissler tube at first continuously, afterwards 
intermittently luminous. After this it was to be expected that 
dry charging-piles could also be constructed of one metal only, 
according to the analogy of Plante's battery. Plates of lead foil 
were coated on both sides with tissue paper, which was made to 
adhere by means of potash waterglass to which a little oxide of 
lead was added. The plates were then cut into pieces of 1 centim. 
square, and, as above prescribed, strung upon a silk thread. A 
pile of 7000 such plates, between the poles of a Holtz machine, 
likewise assumed a very powerful polarization. The action was 
perhaps still more energetic than that of the before-described pile. 
In order that the experiment may be successful, it is requisite that 
the separating layers of paper have a certain degree of moisture, 
which will be produced spontaneously if the pile be left for 24 
hours, under a glass bell, by the side of water. 
The tension falls pretty quickly after charging ; so that sparks 
of 1 millim. length can be obtained only within the first ten 
minutes ; but even after 24 hours free electricity can still be 
distinctly demonstrated at the poles of the pile with the aid of a 
not particularly sensitive gold-leaf electroscope. 
Here also it appears that the products electrolytically deposited 
on the plates by the current (in the present case superoxide of 
lead) act considerably more powerfully than when deposited in 
any other way. A pile consisting of 1000 pairs of lead plates 
coated on one side with chemically produced superoxide and on 
the other with protoxide of lead, gave in the electroscope a 
proportionally much feebler tension. 
As the electromotive force of dry charging-piles never remains 
constant, but, in accordance with the nature of the thing, con- 
stantly diminishes from the beginning, they can never possess any 
practical importance. Nevertheless they are excellently adapted 
to illustrate to a large audience the principle of accumulators. 
The Holtz machine then represents the dynamo-electric machine, 
and the dry pile Plante's or Faure's accumulator : the tension- 
phenomena at the poles are so energetic that they can be seen 
from a great distance. — Wiedemann's Annalen, 1883, No. 7, 
pp. 489-491. 
