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alternating, at intervals of half an inch, with twenty similar zinc 
plates, all united to another metallic bar. He found, on immersing ° 
these plates in the same portion of acid contained in a vessel with- 
out partitions, that, while a wire connecting the poles was intensely 
ignited, only a slight taste was produced on the tongue, not greater 
than that produced by a piece of silver and one of zinc an inch 
square. Hence he concluded that when the plates are arranged 
without alternation the effect is no greater than might be expected 
from one pair of plates. He then caused ten of the zinc plates on 
the one side to be connected with ten of copper on the other, the 
ten remaining plates of the same name on each side being connected 
with each other; the connection between these large plates, one of 
copper and the other of zinc, being effected by a wire. When 
these two alternating pairs were plunged in acid, in a common ves- 
sel without partitions, the wire became vividly ignited. Substan- 
tially, this arrangement was adopted in the construction of a large 
calorimotor ordered by Prof. Silliman for the laboratory of Yale 
College and made under Dr. Hare’s direction. The plates were 
eighteen inches square; nine of zinc, on one side, alternated with 
ten of copper, and ten of zinc, on the other side, alternated with 
eleven of copper; the entire forty plates having in all ninety square 
feet of surface. The plates of the same name were connected by 
large bars of tin, the whole being supported on a balanced frame 
so as to be lowered readily into a cubical box without partitions. 
‘¢ This instrument,’’ says Prof. Silliman, ‘‘ gives no shock, produces 
no chemical decompositions, and does not move the gold-leaf 
electrometer, nor does it ignite charcoal points, however small, 
although in close contact, or strike through the smallest layer of air 
_ to pass even to the best conductor. But when any metallic substance 
with a bright surface is brought into perfect contact, by screwing it 
firmly into the jaws of the vices that terminate its poles, and the 
plates are then immersed in the acid, intense ignition follows and 
combustion also, if the metal is combustible in common air. Plat- 
inum wire is instantly ignited and melted, a large steel knitting 
needle is destroyed before the plates are half immersed, and, by a 
full immersion, iron nails of the size called ninepenny and tenpenny 
are ignited and burn vividly till the connection is destroyed by 
burning in two.’’* Further, it was observed that the calorimotor 
produced fine magnetic effects. 
* Elements of Chemistry, Vol. ii, p. 670, New Haven, 1831. 
