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"If a ray
of the sun's light be admitted through a small hole in the shutter of a darkened room, and be permitted to fall upon a piece of black cloth, which reflects none of the light, the room will appear to be in darkness, notwithstanding the ray of light from the sun passes directly through it. If, however, an orange or other bright object be placed in the ray, the reflection of the light from its surface will not only render the object distinctly visible, but will diffuse light to all parts of the room. Now in this case no more light actually enters the room when the reflecting substance is placed in the ray, but, owing to the peculiar conformation of the surface of that body, it is enabled to decompose the light, and to absorb all the colored rays but the one which gives it its peculiar color ; and that ray it reflects with inconceivable velocity in every direction. If the reflecting substance be removed or destroyed, the room will again become dark, for there will be no longer any object to reflect the rays.
But are we to suppose that with the destruction of that substance the light it emitted is also destroyed ? The presence of light is, indeed, no longer apparent, nor is the substance that reflected it capable of again exerting the same power ; but, nevertheless, the light exists with equal force, and possesses the same properties, though the form of the object that caused the previous sensation of light and color is destroyed. The reflecting substance was only the medium through which the presence of light was manifested to the senses; and though the peculiar properties of the body enabled it to decompose the rays, and to reflect only a portion of the colors that are combined in the white light of the sun, yet those properties produce no effect upon the rays issuing through the aperture until they actually impinge upon the surface of the reflector ; and when that body is destroyed or removed, the light streams onward, unseen indeed, but still existing with the saine energy as when rendered sensible to the visual organs by the agency of a body competent to reflect it.
If we were unable to ascertain that the light in this case is not dependent for its existence upon that of the reflecting body, the phenomenon would strongly countenance the supposition that the light and color must be extinguished with the body by which they are apparently called into existence, and through whose medium alone we become sensible of their presence. We perceive a given substance presenting a certain form and color, and communicating light all around. When that body is destroyed no trace of light remains, and we are involved in darkness. If we were ignorant of the source whence the light is derived, would not the supposition that the light and color are still existing unaltered and undiminished, and that the substance we beheld was not the cause of the light, but was merely endued with properties capable of rendering them apparent, be deemed utterly incredible ? Assuming, therefore, that we were ignorant of the cause whence the light originated under such circumstances, it would, we contend, be equally difficult to imagine the continued presence of light and color in the midst of darkness, as it is, in our admitted ignorance of the nature of the sentient principle, to conceive that it should continue to exist after the dissolu
tion of the body; and the sceptics might raise even more weighty arguments against the former hypothesis than any they are able to advance against the latter.'
The first of these illustrations—which represents the object that reflects the light as unaltered, though rendered invisible by a change in the reflecting powers of its surface—may be considered as symbolical of the condition of a living being in a profound sleep or trance ; when the body retains its vital powers without exhibiting any signs of vitality. The latter illustration-of the continued presence of light and color after the destruction of the reflecting body-may be regarded as representing the sleep of death, and the decomposition of the human frame, whilst the inscrutable, incorruptible essence, that endued it with vitality, survives, independent of the material organization which is requisite to render its existence appreciable by our iin perfect organs of perception.'
In the same manner, Heat is shown to furnish its analogies. The different forms of water, gaseous when decomposed, liquid in its natural state, ice when frozen, and vapor or steam, in another condition, all result from the increase or diminution of heat. This fact of changes or states, is also true of mercury. The resemblances and the differences of light and heat are skillfully pointed out and applied.
When, therefore, we find that these active and intimately connected subtile agents can be separated, and that the balance of evidence warrants the supposition that they are really distinct essences or forms of matter, all objections to the separate existence of the soul from the body, founded upon their intimate connection with each other, may
be overcome ; for in the instance before us we perceive two subtile essencesof whose nature or of the minuteness of whose particles we can form no conception-united so intimately as to appear one and the same, and yet capable of being dissevered and of having separate existences. The union between the sentient principle and the human frame, it must be borne in mind, is a union of two principles that are manifestly distinct, and whether or not we admit that the mind can exist without the body, we must allow that no two conceivable things can exhibit greater dissimilarity than gross substantial matter and the subtile essence, or immaterial principle, which directs and controls it. In the case of light and heat, however, the two subtile essences possess so close a resemblance, that it becomes doubtful whether or not they are identical ; and yet those closely connected properties of matter may, as we have seen, be separated, and exist, apparently at least, in separate and independent states.'
pp. 108, 109. Heat likewise is indestructible. Even when the water passes into a solid form it is not lost. “ Numerous experiments might be adduced to show, that heat is never annihilated, and, that when it is brought from a latent into an active state, it is again diffused by radiation and by conduction to other bodies.” We must pass over Electricity and Galvanism, as we cannot stop to dwell upon their phenomena which are brought into use to aid in his general arguinent. The effect of galvanic electricity on the decomposition of water is given with much success.
• The following example of the suspension of chemical affinity by the influence of galvanism is still more curious. If the wires of the positive and negative poles of a galvanic battery be inserted, the one into an insulated cup containing an alkaline solution, and the other into a cup containing an acidulous mixture ; and if both these cups be connected, by moistened fibres of asbestos, with an intermediate one containing water, the acid in the cup connected with the negative pole will be imperceptibly conveyed by the connecting fibres of asbestos into the intermediate cup, and will be thence transferred to the cup connected with the positive pole of the battery. The alkali will, in the same manner, be transferred from the cup connected with the positive end, and be conveyed through the intermediate cup of water to that with which the negative wire is connected. During this process the acid and alkali, which possess a strong affinity to each other, must have been brought into contact in the intermediate cup of water, and during their passage along the connecting fibres of asbestos, without combining. The water, also, which possesses a strong chemical attraction for both the acid and the alkali, has allowed them to traverse its particles without retaining either; and the result of the experiment is, that the acid and alkali have changed places without any chemical combination having taken place between the three liquids, which possess, under ordinary circumstances, strong reciprocal attractions. The suspension of chemical affinities in this instance, under the influence of galvanic electricity, is quite unaccountable in our present state of knowledge, and presents another fact from which man may learn to doubt the correctness of positive conclusions founded only upon his limited acquaintance with the influences which the subtile—and to him inscrutable-properties of matter may exercise upon the combinations and existences of different bodies. pp. 127, 128.
• Ignorant as we are of the nature of electricity, it is much more cognizable to the senses than any of the subtile properties we have hitherto considered. It can be felt, seen, heard, smelt, and even tasted, and yet we cannot form the most distant conjecture respecting its nature, or by what means it becomes perceptible to the organs of sense.
When, therefore, we find that apparently insurmountable difficulties attend the investigation of the character of an agent that is subject to the examination of all the external senses, the investigation of those more subtile material properties that are not appreciable by any one organ of sensation seems a hopeless undertaking; and we feel that it is not within the range of the highest human intellect to comprehend the nature of the soul, the mysterious attributes of which far exceed those of the subtile properties of matter.' pp. 133, 134.
Magnetism is not less curious or important in its bearings on our author's argument. The division of the forces of the magnet,
its opposite poles,—with the powers of attraction and repulsion, the change which occurs when it is broken,-these with other facis, are utterly beyond our reach to account for.
The property of polarity is essential to the existence of the
magnetic influence, and when a magnet is broken it instantly becomes two separate magnets, each one possessing two opposite poles. This is the case not only when a magnet is broken in the middle, but even when a small portion is broken off the end of either pole. Suppose, for instance, that we had a magnet twelve inches long ; then six inches each way from the centre would exbibit opposite states of magnetism, which would increase in power to the ends of the magnetic bar. Now, if we were to break off one inch from the positive end, the natural inference might be that the whole of that fragment would exhibit positive magnetism ; but instead of that being the case, the fragment immediately possesses two opposite poles ; the fractured part becomes the negative end, and will strongly attract the end of the inagnet from which it was broken, whilst the other end will repel it. After the original magnet has been thus shortened, the neutral point will be removed nearer to the negative end, and that point which, prior to the shortening of the bar, exhibited no signs of magnetism, will then become magnetic.
How the magnetic power in the fragment can divide itself into a positive and negative state it is impossible to conceive ; for, as those two states possess a strong reciprocal attraction, and of course neutralize each other, even if we could form a conception of the manner in which they exist at the opposite ends of the same bar of steel, we should be still at a loss to understand how the magnetic fluid could, when a piece of that bar is broken off, collect itself into a state of excess at one end of the fragment, and leave the other end in a deficient state. The difficulty is increased by adopting the supposition that there are two distinct magnetic fluids ; for in that case, when a piece is broken off the end of a magnet—which, of course, must be charged with one kind of magnetism alone—the sudden appearance in that part of a different and opposite kind of magnetism would be utterly unaccountable.' pp. 140—143.
The conclusion furnishes our author with a fine strain of rebuke to miscalled philosophers, who object against the existence of a sentient immaterial principle, because they cannot comprehend the method of its existence.
• The phenomena of magnetism that we have been considering, become so familiar from frequent observation, that they cease to excite surprise ; but let us for a moment conceive that the properties of the magnet were unknown, and that a traveller from a distant part of the world were to announce the discovery of the loadstone and its singular powers. Imagine, for instance, that he were to communicate, for the first time, that there existed a substance which possessed an attractive power sufficiently strong to lift bodies many times exceeding its own weight, but that this powerful attraction was only exerted on iron ;that this peculiar force was not obstructed in its operation by the interposition of the hardest substances between the attracting power and that metal;—that this wonderful property produced not the least apparent variation in the bodies that possessed it, and that by mere contact it might be communicated to steel, not only without occasioning any loss to the original source whence the attractive power was derived, but with a positive increase to its energy by the communication of it to other substances. Let us suppose our traveller to state, in addition to these circumstances, that when this attractive property was communicated to a piece of steel, the two ends possessed different kinds of attraction, and that one would repel the end which the other attracted ; that if this newly-discovered substance were broken into a thousand pieces, each piece would possess attractive powers, and the opposite ends of each fragment would possess opposite kinds of attraction; and, to conclude his tale of wonder, that if all the pieces were suspended freely, they would all point in the same direction.
We can readily conceive that the traveller who revealed this discovery would be overwhelmed with ridicule, and his statements would be deemed scarcely more deserving of credence than those of Baron Munchausen. If the subject were thought to be worthy a moment's attention, there is not one of the alleged properties that would not be assailed by plausible arguments, founded on fallacious premises, that might serve for the construction of logical syllogisms to prove the existence of such a substance to be impossible. pp. 146—148.
Chemical attraction, the definite proportions in which substances unite with the various and curious exhibitions of the atomic theory on this subject,—the double transfer and the astonishing effects produced, are ably illustrated, dwelt upon and pressed into service by our author.
We have room but for a single illustration.
When an infusion of tincture of galls and a solution of the green sulphate of iron—both colorless transparent fluids—are mixed together, they become black. If muriatic acid be then gradually added, the transparency of the liquids will be restored; but by the addition of a small quantity of colorless solution of potass, the solution will again become perfectly black. By a fresh addition of acid the transparency of the liquid may be again restored, and a further portion of potass will afterwards change it to black. In this case the tincture of galls unites with the sulphuric acid that holds the iron in solution, and liberates the metal in the state of a black oxide, which is held suspended in the fluid, to which it imparts the property of absorbing all the rays of light. The addition of more acid re-dissolves the metallic oxide; and the further addition of potass attracts the acid from the metal, and causes it to be again precipitated. In these experiments we perceive that the effects are produced by the power of elective affinity in the acids, the metal, and the alkali, but in what that power consists, or by what means its operation causes the mixture at one time to absorb all the rays of light,