ON THE INFLUENCE OF FRICTION UPON THERMO-ELECTRICITY. 105 
insensible, and at length seem only active in causing the persistence of the 
maximum of deviation. I found the values of the maxima for different 
couples just in the same proportion as their thermo-electric effects. 
The four above-mentioned facts require an assiduous inquiry, supported 
by numeric determinations. The quantity of permanent heat, which by a 
friction of given duration accumulates in the metals, should be measured, 
and it must be ascertained whether this residue is equal in each of them; in 
other words, whether at the end of a continued friction the needle returns 
precisely to its primitive position, or only approaches to it ; and, if an excess 
of temperature is denoted, in which of the two metals it has taken place. 
Any one who knows the difficulty of managing such delicate instruments, 
will understand why, after innumerable essays, I am not yet able to give a 
categorical answer to these questions. 
After a friction somewhat prolonged the needle does not return imme- 
diately to its original position, but the difference is very trifling, and some- 
times doubtful or ambiguous. Whenever, by a very efficacious friction, I 
had carried the deviation to a maximum of 60°, the needle, on the friction 
ceasing, underwent a vibration of six or eight degrees, but as the slowness of 
these oscillations enabled the temperature to become equal for the two bars, 
the first position of equilibrium remained ambiguous. In one apparatus a 
dise of bismuth was uniformly rubbed during twenty minutes on a disc of 
antimony. When the friction ceased, I immediately inserted between the 
two metals a highly susceptible thermopile, and it appeared by this process 
that antimony was constantly the most heated. Nevertheless, I regard this 
point as not yet fully proved. 
In excusing the defectiveness of my results by the arduous nature of the 
observations required, I consider it my duty to indicate to the philosophers 
who would co-operate in the eminently important tribothermical researches, a 
circumstance which most decidedly contributes to their difficulty. ‘The metals 
to be examined must be joined to the multiplicator by rheophoric wires, and 
these are mostly heterogeneous to the metals, as bismuth, antimony and cobalt 
cannot yet be wiredrawn by any known process. In employing wires of cop- 
per, of platinum, or of nickel, we might hope that their specific action on the 
thermo-electrical elements could be neglected, and that therefore the observed 
deviation might be assumed to result only from the temperature, or from the 
friction of the thermo-electric couple. A course of rather tedious experiments 
has shown me that this supposition is most erroneous and utterly deceptive, 
when applied to refined investigations and highly susceptible instruments. A 
multitude of contradictory and incoherent facts accumulated themselves like 
a chaos, before I arrived at the source of error. Thus, when I broke a bar of 
chemically pure antimony in the middle, and rubbed against each other 
the once contiguous surfaces of these two parts, I obtained very sensible 
deviations, but sometimes positive and sometimes negative. It was the same 
with the bismuth when similarly treated. It appeared at length that these 
strange results were merely owing to the action of the thermo-electrie metals 
on their heterogeneous rheophores, for two copper elements with copper 
rheophores, and two zine elements with rheophores of zinc, never give the 
slightest trace of tribothermo-electric effect, whilst any of these two metals 
produces a strong deviation, when after friction it is singly applied to the 
button of the multiplicator. A voluminous journal of attempts to decide the 
questions treated in the former part of this paper was nullified by the unex- 
_ pected thermo-electric influence of the rheophores destroying its value. The 
best means I ultimately discovered for reducing this source of error, whose 
entire: elimination is impossible, consists in the interposition of a plate cut 
