by inherent qualities, as materialists claim, it matters not in this connection. These molecular changes are the origin of the unit force. The effects of these changes are eternal, imperishable, indestructible. But they are not necessarily incessant. They may be stored up, imprisoned, only to be liberated through the transference of some other influence. As thus: in the early carboniferous ages the force liberated through the changes going on within the sphere of the sun being manifested upon the earth as light, heat, and chemism, induced certain molecular changes here, which resulted in the new combination of the elements of matter then existent, and the consequence was an extraordinary organic growth, and the formation of the carboniferous forests. The continued force, which had its initial point in the sun, still active, but modified by previous changes of the same matter, and by self-limiting, environing circumstances, finally resulted in those immense carbon deposits which to-day form our coal-fields. The coal which burns in my grate is but the imprisoned force which was originally derived from the sun, and which came in the form of light, heat, electrical, and chemical changes. For proofs of this we have but to subject it to favorable influences and there will be returned to nature the same identical light, heat, chemical, and electrical forces which so long lay inactive, dormant, latent, imprisoned within the coal-bed. It is capable of demonstration that the amount returned is the exact amount so long ago received from the sun. But the light, heat, etc., or in other words, the force liberated in my grate is not lost or wasted, but is absorbed, appropriated, perhaps imprisoned within other masses of matter, to be in turn again yielded up and again utilized. Or, perhaps the force so eliminated from the coal is at once made manifest in some other mode of motion, and thus transmitted on and on, now exhibited as heat, now as electricity, and again as light or chemical affinity.

I might enumerate very many instances wherein one manifestation of the unit force is changed into another. I might speak of the heat, the light, and the electricity which in various ways accompany or are the result of all chemical action.

I might show that electricity and light and chemical action are ever attendant upon the development of heat, and that heat and light and electricity are the accompaniments of the development of chemical action; but it is all summed up in the declaration that all movements of matter, in whatsoever way they may be brought about, are producers of the unit force in some one or more of the methods of its manifestation. I cannot open or shut my jack-knife without

the evolution of heat and electricity in greater or less degree. If I bring the blade of my knife in quick, sharp contact with another substance sufficiently hard and brittle, heat and light are made evident to the senses, as in the use of the flint and steel.

to us.

The evolution of force and its methods of manifestation are controlled by definite laws, which are as yet in a great degree unknown Prof. Grove says that the law or rule as to the production of heat or electricity from friction or percussion is that when the mutually impinging bodies are homogeneous, heat is the consequence; but when they are heterogeneous, electricity is evolved, although either is in a greater or less degree the constant accompaniment of the evolution of the other. In fact, it is true that the production of one force or mode of motion is, as a rule, accompanied by more or less of the others. The beautiful photographic process, which is but the conversion of light into the molecular motion commonly known as chemical action, is accompanied by the evolution of heat and electricity, though in quantity not appreciable to anything but the most delicate apparatus. If I bend a poker across a chair-back the molecular disturbance of the iron, if it be measured by thermometers and electrometers of sufficient delicacy, will distinctly show an alteration in temperature and electrical condition, and this is true of every change in the relation of the atoms which go to make up matter.

Matter is composed mainly of four simple elements-oxygen, hydrogen, nitrogen, and carbon. Of these four three are gaseous, and their atoms move freely and with little friction. Many of the compounds of these elements are what are called allotropic, or isomeric— that is, two bodies are composed of exactly the same number of atoms of each element, and yet they are totally unlike, because the relation of the atoms is not the same. Thus the oils of turpentine, lemon, and juniper are chemically the same, yet physically different. So that it is seen that very slight atomic or molecular changes produce wide divergences in the character of compounds. Then, too, there is abundant opportunity for such changes to be brought about by a very slight exertion of force. The compounds of nitrogen (and this includes all the so-called albuminoids) are very mutable, and are ever seeking for some more permanent union. The exhibition of the slightest force is sufficient to induce a disruption of imprisoned chemical affinities, which may result in wide changes.

Again, compounded matter exists in a number of forms, as gaseous, liquid, and solid. Of these the first two are easily impressed, and

molecular changes are constantly going on. Solid matter exists in two different states-the colloid and the crystalloid. Of these the first is unstable and exceedingly mutable. So that of all the forms. in which matter exists, there is but one in which it is not easily changed and made to assume new molecular conditions. We have shown that every such molecular disturbance, however induced, is followed by the evolution or the transference of some one or more of the various manifestations of force. Given, then, that most forms of matter readily undergo molecular and other changes, and that the manifestations of existent force, such as light, heat, chemism, etc., are constantly active, and that such action can only result in still another transference of force, it may readily be seen how unceasing must be the phenomena presented by all these mutations and mutually-induced changes. Every wave of force exerted at the initial period of this universe has been since that time and ever will be existent, and either constantly, actively exerted, or passively imprisoned by superior force. Matter is, under the action of force, constantly being disintegrated and its constituent particles built anew into fresh forms. And so this tearing down and redistribution of matter is, under the dominion of force, constantly going on. Every organized being, whether animal or vegetable, has its period of molecular aggregation, of growth and socalled nutrition, of active, progressive changes, and then the same forces which have resulted in the combination of the molecules which make up its substance, are again active in those yet further molecular changes which bring about its morphological destruction. I say the same forces which brought together the molecules which compose this body of mine, will in time insure their separation, and thus bring about the disintegration of solid and fluid tissues, and return them again to the common stock of matter, while the energies which brought about these definitive changes, through the reaction of the matter thus metamorphosed, will in turn be transformed into other forces, and itself returned again to the parent or unit force whence it was segregated, and thus will all that which goes to make up this Ego, this individual I, be returned again to that great source from which it emanated.

If this doctrine of the unity and the correlation of forces be admitted as true in its application to the various forces of which we have been speaking, are we not justified in assuming that the law is general throughout the material universe? And whether we study this unity as exhibited in the macro-cosmos, or in the micro

cosmos-in the revolutions of solar systems, or in that affinity which binds together two atoms; in those early convulsions which resulted in the upheaval of continents, or in the change which culminates in the growth of a blade of grass; in the devastating earthquake, or in the fall of a leaf in autumn; in the whirling in infinite space of a planet, or in the infinitesimal vibrations of a ray of light; in the action of volcanic fires, or in the molecular changes within the single battery-cell, we shall see that in any extreme it unfailingly exhibits the same characteristics. It is the exhibition of the same force which results in the molecular aggregation called man, and that of the lowest organic life. Within the two organizations constant molecular changes are going on that differ but in degree. The results of those changes in the two are precisely alike in fact. Life-vitality— in the one is, in a physical sense, precisely what it is in the other, except that in the lower it is simple, and all the processes are elementary; in the higher it is complex, and not readily comprehended. And now, having considered the law of the correlation of forces in its application to the lower forms of matter, shall we stop when we are just upon the threshold of the secret places of nature? We have shown that in inorganic life the law prevails and explains all the phenomena there exhibited; shall we admit that the harmonies of nature become discords when they are played upon the strings of a more perfect instrument? As we rise in the scale of existence shall we conclude that, where before all was beauty and harmony and exactness, now all becomes discord and falsehood and incongruity? Shall we admit that the laws which are universal in the lower objects are suspended when we arrive at the point where they are most needed to make things congruous? The world has long accepted as a fact the belief that man is a law unto himself, and that his physical being is not subject to the rules which govern all the rest of creation. The life of one of the lower animals was thought to be one thing, that of man to partake of a very different essence; that the vitality of the shrub which grows by the wayside had no kind of resemblance to the flower which blooms in our gardens. Let us look into this thing.

My subject, as announced, is Nervous Force. Perhaps many of you have wondered if I were to pay it the respect of a passing glance, and if so what my long prelude meant. It was necessary that I first establish and make clear to your comprehension the doctrine of the correlation of forces before I attempted to apply it to other and higher uses.

We have seen that the light and heat of the sun, under favoring conditions, have developed or been transformed into other forces. We have examined those forces, and have found them a unit in their origin, though diverse in their mode of manifestation. We have seen that light may be changed into heat, heat into electricity, and that into chemical affinity; that all these so-called forces are mutually interchangeable, alike, identical; that each is the result. of certain molecular changes, themselves induced by manifestations of other varieties of the unit force. We know that all organic bodies, whether of low or high degree, are composed of the same atoms that unite to form other matter, and therefore they must be amenable to the same laws.

There are certain phenomena connected with living matter called vital phenomena. Under the old hypothesis, that there were many kinds of force, and that each was an entity, acting in an independent manner upon such matter as was subject to its influence-it was easy to suppose that nervous force was a something distinct and by itself, and that it was not subject to the laws which governed other forces. When it was believed that magnetic attraction was a pervading something which established a kind of affection between certain substances, and aversion toward others, and that this attraction was a thing by itself, dominated only by its own laws, and owing no allegiance to the ordinances which governed the relations of other matter, then it was easy to imagine that nervous force was a principle alike distinct, separate, and removed from all other dominant forces. In that early day there was no harmony in nature, but a continual clashing and discord among mutually-contending forces. Let us now suppose that nervous impulse is but another mode of manifestation of the unit parent force, and how quickly all becomes harmony and beauty.

The lapse of time admonishes me that I cannot pursue this inquiry with all the minuteness with which I endeavored to examine the physical forces; but that all force is identical, interchangeable and the same, seems to me plain for a number of reasons. In the first place, it is derived from the same source. The same molecular changes and mutations which in the battery-cell result in the evolution, or more strictly speaking, the segregation, of electrical force, are here manifest as nervous force. We are constantly supplying the elements of this nervous battery in the food which we take, and those molecular changes which we denominate digestion and assimilation result as such changes ever do and must result, in the elimination of a