ON THE INFLUENCE OF FRICTION UPON THERMO-ELECTRICITY. 107 
and cold when travelling inversely, by which M. Lenz has produced conge- 
lation ? 
The electric telegraph is becoming popular at present, but it generally re- 
quires an apparatus which is variable in its effects and expensive in its employ- 
ment. It would therefore be advantageous to substitute the purely mecha- 
nical principle of the tribothermic telegraph. For by removing the stopper 
of a wheel-work, a disc of bismuth rubs against another of antimony, and 
at the same instant the needle at the opposite extreme of the rheophore is 
put in motion. I have ascertained the instantaneousness of this operation for 
tolerably considerable distances. Employed as a signal, it would have the 
advantage, that after the interval of some days or months, when the clockwork 
is put in motion, the effect of friction would take place, whereas in the vol- 
taic telegraph there would be a chance of the combination having lost its 
efficacy by the lapse of time. 
P.S.—Berlin, August. A highly competent judge (Mr. Grove) being of 
opinion that I have imperfectly explained the grounds for my suspicion of a 
possible analogy between certain effects of the heat which is generated in the 
act of friction and the discovery of M. Peltier, I regret that in my paper I have 
affected a form too strictly aphoristic. I shall endeavour to remedy this by 
selecting, among many others, one tribothermo-electric fact, whose very para- 
doxical character first induced me to suppose such an analogy. Let a erystal 
of sulphuret of lead (galena) be placed at one of the poles of the multiplier, 
and at the other pole (to be alternately placed in action) of the rheophore a 
bar of bismuth and a bar of antimony ; the bismuth being rubbed against the 
crystal, takes immediately a negative electric charge. This exception was 
already known for the same metal heated. Fromall the analogies hitherto 
known, it results that antimony being rubbed in the same way should become 
positive, and that to obtain by it a negative declination of the magnetic needle, 
it ought to be refrigerated. Now I find by experiment that the friction of 
antimony against a crystal of galena gives absolutely the same declination as 
the bismuth: in fact, the direction, the intensity and the quickness of the 
effect, are in the two cases sensibly equal; and we cannot deny that in this 
very paradoxical case, it appears that an increment of nascent heat produces 
in the antimony the effect of cooling. The singular effects which are ob- 
served when uncrystallized masses of sulphuret of lead are substituted for the 
single crystal of galena, confirm the supposition that the effects of friction 
depend on molecular movements. I am anxious that more practised observers 
may succeed. in obtaining tribothermical effects by simple internal vibration 
of elastic sound-plates. I have not yet succeeded in this. But the great 
prize in this race of discovery would fall to him who should discover a dif- 
ference of thermo-electric action, according as a magnetically polarized bar 
should be rubbed (that is, molecularly heated) at the one or the other of 
its poles. 
The magnet-stone and the magnetic sulphuret of iron, exert, when rubbed, 
a strong thermo-electric action. I have employed these substances, as well 
as magnetic steel bars, in this curious investigation, but hitherto without 
success. 
Utter 
