Conservation and Innovation : Helmholtz's Struggle with Energy ...

"a series of important and difficult experiments on the relation of heat
to mechanical force, which supplied the chief points in which the comparison of
the new theory with experience was still wanting" 342.
Joule's experiments are actually given great attention, in contrast with
the 1847 Erhaltung. This time, of course, the conversion factors are correct. For
the determination of the equivalent through the production of heat from work
utilising friction, three series of experiments are recalled: water in a brass vessel
(equivalent=424.9 gramme-meters necessary to raise of one degree °C one
gramme of water), mercury in an iron vessel (425 and 426.3), conical rings
rubbing against each other surrounded by mercury (426.7 and 425.6). The reverse
determination, that is, the conversion of heat into work through the expansion of
perfect gases, is also discussed; results (also due to Regnault's measurements)
give : with air 426.0; with oxygen 425.7; with nitrogen 431.3; with hydrogen
425.3.
The agreement between the two set of experiments, realised with such
different methods is really remarkable. There can be few doubts that "heat is a
new form in which a quantity of work can appear" 343.
A comment on the presentation of the principle is necessary here: the
expression of the principle above 344 shows once again that the stress is on the
correlation of forces, but Helmholtz goes even further in hiding his own
conceptual model of central forces that had played such a great role in the
original Erhaltung . In the extension of the law to all natural processes, the
question of the nature of heat became specially important. "In the answer lay the
chief difference between the older and newer views in these respects". Moreover
in virtue of the relevance of this question:
"Many physicists designate that view of Nature corresponding to the
law of conservation of force with the name of the Mechanical Theory of Heat" 345.
Thus Helmholtz stresses an element, the conceptual model of heat,
which despite being universally acceptable and also accepted, was by no means
his own specific contribution to the problem. After an acknowledgement of the
results of the kinetic theory of gases due to Krönig, Clausius and Maxwell 346 and
342 Helmholtz PL 1873 p.320.
343 Helmholtz PL 1873 p.349.
344 See note 340.
345 Helmholtz PL 1873 p.342.
346 Helmholtz PL 1873 p.350.