Electromotive Forces in the Voltaie Cell. ~ 
the original man replies, and so there is a controversy, and 
nothing is really settled at all. Finally, some one else in- 
dependently goes over the whole ground from some distinct 
point of view, makes a few well-planned, clear, and decisive 
experiments, describes them in a compact and readable form, 
and there results a definite gain to science. But how much 
better would it have been if this last paper had been the only 
one published! Unless a man is an experimental genius of 
the highest order, it is necessary for him to think for far 
more time than he experiments, if he wishes to advance and 
not to lumber his science. If it be objected, as indeed it may 
with great truth be, that one man’s life and capacity are not 
sufficient for this in the present state of knowledge, the ob- 
jection constitutes a strong argument in favour of the pro- 
position that the time has come for an organization of science 
and a more definite division of labour. 
To return to the experiments of Herr Schulze-Berge, one 
is not able to say after all that they are very satisfactory, for 
they do not distinctly settle any question. The general con- 
clusion he draws from them is the apparently safe one that 
the contact-force between a metal and a gas is not in general 
the same as between a metal and air. LHven this is not ab- 
solutely safe, however, because it might conceivably be that 
an airjgas contact-force caused all the difference. Granting 
that this is unlikely, the experiments are in favour of a con- 
tact-force between metals and air or gas; but they do not 
establish the fact any more strongly than, if so strongly as, 
Mr. Brown’s experiments had already done. ‘The weak point 
in both is the possible corrosion of the plates and formation 
of films of alloys or compounds, which may be the real source 
of the observed difference of potential. 
And against the existence of a contact-force between metals 
and various gases, the experiments of Pellat and others are to 
be remembered, which resulted in the conclusion that a con- 
denser made of two different metals showed nearly the same 
Volta effect, whether the atmosphere surrounding the plates 
was air or hydrogen. 
If it be assumed that the experiments of Brown and Schulze- 
Berge establish their point, and that Pellat’s apparatus for dif- 
ferent gases (fig. 9) is satisfactory (rather a large assumption), 
Iam unable to reconcile the discrepancy, except by suggesting 
that Pellat did not take sufficient pains to remove the con- 
densed-air sheet originally on both his plates. It is of course 
' just possible that the difference between the potentials of the 
two metals might be the same in two gases though the absolute 
potential of both was different, but it is improbable. 
