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

But was important here is that despite the fact that, in the late seventies, no
conclusive evidence existed for a specific theory, Helmholtz came gradually to
consider dielectric theory as correct.
"In the Faraday lecture of 1881 he predicted the decline of action-at-a-distance
on the Continent and lent full support to Maxwell’s theory" 405.
But he was still convinced, against Maxwell, that electricity consisted ultimately
in discrete charges, "atoms of electricity". Thus the main element accepted from
Maxwell was the role of the dielectric and, gradually, contiguous action.
Helmholtz’s shift towards contiguous action and, in particular, the relation of the
shift with the new version of PCE (Poynting's principle of local conservation)
deserves detailed attention. Helmholtz’s views at the beginning of the eighties
had already undergone some changes. His 1847 Newtonian model of central
forces depending only on positions was changed in 1870 into a model of forces
and torques. The theory of the dependence of forces on the positions was also
lost, when Helmholtz accepted the general electrodynamic potential, a concept
first introduced by F.Neumann, Weber and Clausius. In 1872 Helmholtz asserted
the further condition on PCE, i.e. that the generalised kinetic energy of the
electrical system (deriving partly from electrodynamic potential) must always be
positive. Very few aspects of Helmholtz’s early conception remained at the
beginning of the eighties. One of these was the distinction between kinetic and
potential energy. While shifting towards contiguous action, a conception that in
the end would have denied this distinction, Helmholtz underwent a second,
almost contemporary, shift: the Principle of Least Action was now to be
considered the key to physical research, more than the Principle of Conservation
of Energy.
Unification, again ( 1884-94)
In a long paper of 1886, Helmholtz introduces a new unifying
programme in physics, based on a heuristic principle different from energy
conservation : the principle of least action (PLA). The principle of conservation
of energy is abandoned as the main guide in physics :
"it in fact holds in a great variety of cases when least action does not.
The latter is thus more specific".
405 Turner, Steven. "Hermann von Helmholtz." In DSB 6 ,1973. Pp.241-53. P.252.