121 
pairs of two feet eight inches by six feet and the two thousand 
» four-inch pairs of the Royal Institution, the phenomena indicate 
the presence of both fluids. In De Luc’s column, where the size of 
the plates is insignificant and the energy of interposed agents feeble, 
we see electricity evolved without any appreciable quantity of cal- 
oric. In the calorimotor, where we have size only, the number 
being the lowest possible, we are scarcely able to detect the presence 
of electricity. When the fluid contains enough electricity to give 
a projectile power adequate to pass through a small space in the air, 
or through charcoal, which impedes or arrests the caloric and favors 
its propensity to radiate this principle, heat is evolved. This ac- 
counts for the evolution of intense heat under those circumstances 
which rarefy the air, so that the length of the jet from one pole to 
the other may be extended after its commencement. Hence, the 
portions of the circuit nearest to the intervening charcoal or 
heated space are alone injured ; and even non-conducting bodies, 
as quartz, introduced into it are fused, and hence a very large wire 
may be melted by the fluid received through a small wire impercep- 
tibly affected.” 
To these two forms of galvanic generators, which differed as ma- 
terially in the effects which they produced as they did in their con- 
struction, Dr. Hare gave the names ‘calorimotor’’ and ‘ defla- 
grator.’’ The calorimotor was constructed first in 1818. He was 
led to this form of instrument by reflecting that, ‘‘as the number 
of pairs in Volta’s pile had been extended, and their size and the 
number and energy of interposed agents lessened, the ratio of the 
electrical effects to those of heat had increased till, in De Luc’s 
column, they had become completely predominant ; and, on the 
other hand, when the pairs were made larger and fewer (as in Chil- 
dren’s apparatus) the calorific influence had gained the ascendency ; 
he was, therefore, led to go farther in this way and to examine 
whether one pair of plates of common size, or what might be 
equivalent thereto, would not exhibit heat more purely and demon- 
strate it to be, equally with the electric fluid, a primary product of 
Galvanic combinations.’’* This conception he put into practice 
by constructing a single galvanic pair, consisting of twenty copper 
plates, each about nineteen inches square, all soldered to the same 
metallic bar, so as to constitute, electrically, a single copper plate, 
* Amer. Jour. Science and Arts, i, 416, July, 1818. 
PROC. AMER. PHILOS. SOC. XXXII. 148. P. PRINTED DEC. 18, 1893. 
