Dr. (late Professor) James D. Forbes (' Reply to Tyndall on Rendu ') has already noticed the futility of these claims; but what he, by the free application of meiosis, calls "the theoretical inferences of Messrs. Grove and Helmholz," Faraday, as we have seen, accepts as demon strated principles of nature, and Professor Le Conte, we shall presently find, regards as forming "a necessary truth," and "one of the grandest generalisations in modern science." Two remarkable circumstances have characterised the history of the reception of Mr. Grove's doctrine of correlation. Many physicists and others who admit in a general manner the principle, seem very unwill ing to use the term ; while others who explicitly adopt and advocate both, seem equally unwilling to ascribe them to their author, and omit all reference to him.
Thus, in Professor Lie biTs 'Familar Letters on Chemistry' (1858), in the preface to the fourth edition, the introduction of a letter (the I3th) On the Correlation of the Forces of Inorganic Nature,' is announced in the preface, but neither in that nor in the letter itself is Mr. Grove mentioned, nor indeed are his views given, though his designation of the subject is thus unreservedly employed. It is applied, in the letter, chiefly to a view of natural forces taken by Dr. Mayer of Heilbronn, asserting both their indestructibility and their converti bility, as consequences of the axiom Cauca trquat effectum, but not dated, and apparently subsequent to tho views both of Helmholz and of Grove.
The following introductory paragraph of an excellent paper by Professor Le Conte, of South Carolina College, Columbia, U. S., the Correlation of Physical, Chemical, and Vital Force, and the Con servation of Force in Vital Phenomena,' contains ono of the most emphatic and adequate recognitions of the importance of those princi ples and intelligible terse statements of their nature which has yet appeared ; though, even in this, no allusion is made either to Mr. Grove or to M. Helmholz, and the uninformed reader might be led to suppose that being necessary truths they had always been self-evident. "Matter constantly changes Its form, but is itself indestructible, except by the same power which called it into being. The same quantity of matter exists in the universe at all times. So also force changes its form constantly, but is itself indestructible, incapable of increase or diminution, and the same absolute amount of force exists in the universe at all times and for ever. The mutual convertibility of the various forms of force is called ' correlation of forces.' The invariability of the absolute amount in the midst of constant change is called ' conservation of force.' This principle of correlation and con servation of force must be looked upon as one of the grandest in modern scienee,—a principle startling at first, but when clearly understood and firmly grasped, almost axiomatic. It must be considered a necessary truth, and, as such, is a legitimate basis of deductive reasoning. The correlation of physical forces is universally recognised as a principle In science, and not only so, but has already been productive of many beautiful and useful results."
For Professor Le Grate's application of the principle to the history of organic, nature, we must refer to the paper itself. 'Amer. Journ. of Science,' Nov. 1859, reprinted in' Phil. Meg. Fourth Series,' voL xix., p. 133.
Again, In the introductory address delivered on the opening of St. Thomas's Hospital Medical College, Southwark, London, on the 1st of the present month (October, 1660) by Mr. It. D. Grainger, F.R.S., which has the emphasis of being also a valedictory address on his retirement from the chair of physiology in that school, we find the following passages, which are here cited, not merely for the purpose of claiming for Mr. Grove what of right belongs to him, but because we have in them the sentiments of an eminent physiologist on the cor relation of the vital and physical forces. " In the case of the forces implicated respectively in inorganic and organised bodies, it may in the present state of knowledge be very difficult to demonstrate their ultimate identity. Nor need this be a matter of surprise when we recollect how very recently the intimate relations of the several physical forces themselves have been discovered by such researches as those of Oersted, Faraday, and Graham. Chemical force, electricity, magnetism, caloric, and light, act and react on each other in the mode signified by the term correlation, and are probably, as many profound philosophers suppose, only different manifestations of one universal all prevading force." Proceeding next to the organic forces, the expert meats of Matteuci on the nervous and muscular forces are noticed, together with Dr. Todd's proof that the latter is not itself electricity, the evidence of which is stated to be afforded by " phenomena the very counterpart of what Professor Minter pointed out years ago, in regard to the nervous and electric forces." " Now, although," Mr. Grainger continues, "this may seem to indicate an ultimate and essen tial difference between the electric and muscular currents, it presents the very same condition of things as that expressed by the term ' correlation of forces" Farther on he alludes to the maxim, that there is no creation of force, observing that " no force is ever manifested without an equivalent change of matter, which change, according to the wide generalisation of one of our former colleagues, my friend, Dr. Leeson, is in every form—light, electricity, magnetism, gravitation, &e.—ultimately resolvable into motion." ' Lancet,' 1860, vol. ii. p. 352, 353, Whether Dr. Leeson's generalisation was enunciated prior to Mr. Grove's we are not aware ; but it is simply one elementary correlation of the latter. The reader will have observed that while the doctrine, as well as the designation, of the correlation of forces is fully adopted, Mr. Grove's name is not mentioned; nor does it occur anywhere in Mr. Grainger's address.