604 FRAGMENTS OF SCIENCE. 
tance from its origin. You will be disposed, and rightly 
disposed, to refer those distant manifestations of power to 
the heat communicated to the face of the pile, but the 
case is worthy of closer examination. In 1826 Thomas 
Seebeck discovered thermo-electricity, and six years sub- 
sequently Peltier made an observation which comes with 
singular felicity to onr aid in determining the material 
used up in the formation of the thermo-electric current. 
He found that when a weak extraneous current was sent 
from antimony to bismuth the junction of the two metals 
was always heated, but that when the direction was from 
bismuth to antimony the junction was chilled. Now the 
current in the thermo-pile itself is always from bismuth to 
antimony, across the heated junction a direction in which 
it cannot possibly establish itself without consuming the 
heat imparted to the junction. This heat is the nutriment 
of the current. Thus the heat generated by the thermo- 
current in a distant wire is simply that originally imparted 
to the pile, which has been first transmuted into electricity, 
and then retransmuted into its first format a distance from 
its origin. As water in a state of vapor passes from a boiler 
to a distant condenser, and there assumes its primitive 
form without gain or loss, so the heat communicated to 
the therrno-pile distills into the subtler electric current, 
which is, as it were, recondensed into heat in the distant 
platinum wire. 
In my youth I thought an electro-magnetic engine which 
was shown to me a veritable perpetual motion a machine, 
that is to say, which performed work without the ex- 
penditure of power. Let us consider the action of such a 
machine. Suppose it to be employed to pump water from 
a lower to a higher level. On examining the battery which 
works the engine we find that the zinc consumed does not 
yield its full amount of heat. The quantity of heat thus 
missing within is the exact thermal equivalent of the 
mechanical work performed without. Let the water fall 
again to the lower level; it is warmed by the fall. Add 
the heat thus produced to that generated by the friction, 
mechanical and magnetical, of the engine; we thus obtain 
the precise amount of heat missing in the battery. All the 
effects obtained from the machine are thus strictly paid 
for; this " payment for results " being, I would repeat, the 
inexorable method of nature. 
