and see how the flame shoots aloft in a wavy pyramid of purest emerald,—or change the substance, and lo! undulating spires of loveliest ruby or amethyst,-burning with so celestial a brilliance and transparency as if freed from every tinge of earthy matter, and re-shining with the splendour of its native skies. Or take the living light itself, and refract it through prisms of crystal, and see how the dissevered tremors of the ray reappear on the screen in a band of many-hued light,―red, blue, orange, green, yellow, and violet, blending into each other by most delicate gradations, and all glowing with a richness. which no mortal pencil can copy. Substitute for this crystal prism, one of diamond,-suppose the Koh-i-noor, that "mountain of light," used as a refractor of the sunbeams—as a breakerup of the symmetry of the solar ray,—and then imagine how brilliant would be the spectral colours thus produced. The lustre of the diamond, the topaz, the ruby, the emerald, the amethyst, is well known,-but how comes that lustre which so distinguishes them from other substances? It is because they, of all earthly substances, are the most ethereal in their structure, and hence vibrate and sparkle most readily in unison with the solar rays. Take a large diamond out of the sunlight into a dark room, and you may see it still lustrous for a few moments, because its particles are still vibrating. All substances-air, water, wood, and rock-consist of identically the same atoms, only variously arranged; each possessing different qualities according to the closeness and form in which the particles of their molecules arrange themselves. Thus carbon, when in its amorphous state, is charcoal; when crystallised in prisms, it becomes black and opaque graphite; and when crystallised in octohedrons, it is etherealised into the limpid and transparent diamond. Gems, in truth, are of all earthy substances the most similar in atomic structure to the ether,-to that pure and subtle fluid pervading all space, which gives birth to the lightning, and whose vibrations are Heat and Light. They are formed in the veins of the rock by the slow

and continuous action of electric currents, which, in the lapse of ages, gradually alter the arrangement of the ultimate atoms of the rock, crystallising them in forms congenial to their own ethereal structure.

Science can imitate in some degree this rarest and most beautiful of nature's processes. "There is strong presumptive

evidence," says Mrs Somerville, " of the influence of the electric and magnetic currents on the formation and direction of the mountain-masses and mineral veins; but their slow persevering action on the ultimate atoms of matter has been placed beyond a doubt by the formation of rubies and other gems, as well as other mineral substances, by voltaic electricity." What flowers are to the vegetable world, gems are to the mineral. Both of them are embodiments of the beautiful,-but the latter are of a purer substance, and, if slower of growth, only the more imperishable.

A science of Colour must be based upon a correct theory of Light. We believe the foundations of such a theory already exist. The carefully-conducted though much-contested experiments of Von Reichenbach tend to show that all polarised bodies -such as magnets, crystals, and the like—give off a subtle light of their own, which becomes visible in a dark room to persons of a sensitive nervous organisation. We certainly know that the Earth radiates a light of its own, as exhibited in the beautiful corruscations of the aurora-borealis and the zodiacal light;—the explanation of this phenomenon being, that our planet is a large magnet, through which, as in all polarised bodies, there is a constant passage to and fro of electrical currents, which ray off in light from the poles. I make bold to say that it will ere long be discovered that every planet is luminous, although its light may be overpowered by that of some larger orb,—even as

taper's light is unnoticed in the full blaze of the sunlight; and one of the most fundamental canons in optics will be, that every body radiates more or less of light when its particles are in a state of electrical vibration. The sun and its planets being

in opposite states of polarity, a constant magnetic efflux is flowing from each to the other. This efflux occasions a thrill, or vibratory motion, in the ether which fills the interstellar spaces, and the result of this vibratory motion on the eye is Light; just as a spark, or continuous stream of light, is the concomitant of a similar flux from an electric-machine.

Under the full blaze of the sunlight, the Earth throbs as with a million pulses. Those substances which are most ethereal in their atomatic structure, such as glass and crystals, vibrate most readily and most powerfully; but all things, even the most amorphous in structure, join more or less in the electrical pulsation, transmitting, reflecting, and modifying into colours, the limpid light which streams from the sunny skies. When the sun sets, this vibratory motion of the earth's surface to a great degree ceases, is feebly kept up by the cold radiance of the moon, or fades almost into quiescence beneath the tremulous light of the stars. Put out the stars, and all seems absolute darkness. But is it so? I trow not. Draw the thickest curtain of cloud over the sky-let neither moon nor star, nor feeblest glimmer of the violet-coloured skies of night, break the darkness; and yet, while men grope and stumble, and call to their aid the appliances of luciferous art, myriads of the lower creation-birds of the air, fish of the sea, and prowling and creeping things without number-ply their life as easily as if with them it were not night but day. What does this show, but that Light and Darkness are but relative terms-that what is Night for man is Day for some other creatures—and that even in the night-time the surface of the earth is vibrating, far too feebly indeed to excite vision in man, but sufficient for a vastly wide range of animal life, to whom eyes have been given extremely susceptible to the ethereal vibrations? The great Creator has furnished each class of his creatures with visual organs fitted for their peculiar sphere of action; and man, made for the day and the sunshine, has eyes whose range of discernment is limited to the diurnal phenomena. His organ of sight is adapted for a

certain degree of light, more or less than which tends equally to blindness. He is not more baffled by the shadows of night than by a superabundance of the illuminating rays. Light itself may become darkness. The eagle gazes undazzled on the orb of day; but to us, the sun in its noontide splendour is an invisible spot in the sky; and "dark from excessive bright,” is a phrase not more poetic than true. Since, then, our range of vision is thus limited, let us beware of dogmatising as if light were a word of absolute instead of relative significance;—and although we may not be able to see what Reichenbach's sensitives saw, still less to walk by the feeble rays which suffice for the lower creation, let us confess that the auroral and zodiacal lights, as well as all sound reasoning, show that Earth has a light of her own, by which it is as seemly that some orders of creatures should walk, as we, children of light and of the day, by the nobler radiance of the sun.

It is known to men of science that every part of nature, even the hardest and most solid, is in a state of molecular motion,-so subtle, as in most cases to defy ocular scrutiny, yet indubitably revealing itself in its effects.* It is only when those vibrations grow strong and frequent that they become perceptible to our senses; and then they do so in the form of those ether-born twins, Heat and Light. Let us examine the spectrum, and see how this vibratory motion exhibits itself in the production of Colour. To the ordinary eye, the spectrum, produced by refract

"Nothing can be more certain," says Mrs Somerville, "than that the minute particles of matter are constantly in motion, from the action of heat, mutual attraction, and electricity. Prismatic crystals of salts of zinc are changed in a few seconds into crystals of a totally different form by the heat of the sun;-casts of shells are found in rocks, from which the animal matter has been removed, and its place supplied by mineral;—and the excavations made in rocks diminish sensibly in size, in a short time, if the rock be soft, and in a longer time when it is hard: circumstances which show an intestine motion of the particles, not only in their relative positions, but in space, which there is every reason to believe is owing to electricity, -a power, which, if not the sole agent, must at least have co-operated essentially in the formation and filling of mineral veins."-Physical Geography, I. chap. xv. p. 288-9.

ing or breaking up the symmetry of the solar beam, is merely a series of hues, beginning with red, brightening into yellow, and then fading away through violet into darkness. But if you examine it scientifically, you will find that those bright hues are produced by a series of tremors or vibrations of the broken ethereal ray,—the strongest and therefore slowest of which vibratory rays are least refracted, and form the red, and the feeblest and most rapid are most refracted and form the violet. But the whole of the broken rays are not represented by the colours which meet the eye in the spectrum; for at either extremity, where the red and violet fade out of sight, a succession of rays spread out, invisible to our eyes, but which might be to some extent discernible had we the night-eyes of some of the lower animals. The invisible rays at the red end are the strongest and rarest in the spectrum,-only showing themselves by giving out heat, and an electricity which is positive; those at the violet end are the feeblest and densest,-only showing themselves by their chemical or actinic properties, and by an electricity which is negative. Thus the spectrum exhibits a complex phenomenon. Firstly, we have a series of rays steadily increasing in rapidity and weakening in force of vibration, from one end to the other: (similar in this respect to the atmospheric vibrations which produce Sound, which, emerging from silence as the spectral colours emerge from darkness, run through the scale of the musician, getting quicker and feebler in their vibrations, until they again become inaudible—the ear hearing sounds, as the eye sees colours, only so long as the vibrations continue within a certain range of velocity and force, which varies somewhat in different individuals and animals,-the savage Indian, for instance, hearing sounds and seeing objects where we can see or hear nothing; and dogs and the lower creation exhibiting the same powers to a still greater extent.) But superimposed upon this steadily ascending gamut of vibrations, we have another phenomenon—namely, that one-half of the rays of the spectrum are electrically positive and give out heat, and that the other