SUN-DIAL OF AHAZ.

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palace, so constructed that the rays of the sun fell on them during the day, throwing the shadow in different directions. This, it is thought, was noted in the various stages of its progress, and divided into spaces, sufficiently accurate to determine the larger Jewish divisions of time. Others conclude that it was an obelisk, set up in some open court of the palace, from which, as from a centre, different lines were drawn, at spaces determined by the course of the sun, and thus rendered descriptive of the passage of time. Others assign to it, however, the form of ancient instruments of that kind, usually divided into three parts, and containing some smaller degrees.

But, whatever was this seem that it stood within the afflicted monarch lay. He had cast many a mournful glance on the glorious orb changing its course, for Isaiah had before entered the palace, to pronounce on him the sentence of death. What then could be more impressive, or more delightful, under these circumtances, than the seal of the Divine promise, afforded by the miracle performed? The shadow which had descended ten degrees on the dial, recedes and returns in the same proportion! Most happily did the sign accord with the gracious interposition.

measurer of time, it would sight of the chamber where

A still more remarkable fact is connected with the cru

cifixion of Christ. The evangelist Matthew says: "From

the sixth hour there was darkness over all the land unto the ninth hour." Matt. xxvii. 45. That this gloom was wholly preternatural, and not an eclipse of the sun, is placed beyond all doubt. It happened at the feast of the passover, which was celebrated only at the full moon, a time in which it was impossible for the sun to be eclipsed; such an event occurring only at the time of the new moon. No wonder that a spectator of the miracle is said to have observed, "Either the God of nature suffers, or sympathises with the sufferer." It gave a signal proof of the Divine displeasure against sin. Who does not see, by this darkness, the world called to gaze on the sufferer, and to inquire for what he submitted to death? All have, by transgression, forfeited the light of heaven,-one of the choicest gifts of God, and which opens to us all the glories of his works, and exposed themselves to the woes of eternal darkness. With what earnestness of desire, then, should we, individually, be found seeking salvation! Jesus came "to give his life a ransom for many." Wherefore "he is able to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them." Heb. vii. 25.

CHAPTER IV.

WHAT IS LIGHT-THE MOSAIC NARRATIVE ILLUSTRATED

REMARKABLE FACTS.

To human nature there is something so congenial in light, and so repulsive in darkness, that it is probable on this account alone the aspect of inanimate things is either grateful or the reverse, from its reminding us of one or the other. Thus, perhaps, particular colours throughout the range of our observation are more or less acceptable as they approach nearest or recede farthest from the character of this element, whether reflected directly from the heavenly bodies, from the azure of the sky, or from the brilliant hues with which the rising or the setting sun arrays its attendant clouds.

"In illustration of this principle," says Dr. Kidd, "gold and silver among metals might be opposed to lead and iron; and, among flowers, the brilliancy of the crocus, the lily, or the rose, to the lurid aspect of henbane or belladonna: and though something of a moral character may in these instances determine the preference,

yet there is nothing unreasonable in supposing that, as the instincts of the inferior animals regulate their tastes and distastes to natural objects, so there may also be, in the case of human beings, congruities or the reverse, between the sense impressed and the object impressing it. In fact, with respect to that sense the organ of which is the ear, it is known that infants shrink back from deep sounds, and express delight at acute sounds, long before any intellectual or moral feeling can sway them; and, correspondently with this assertion, the lullaby of the nurse partakes, among all nations, of the same essential character. is a fact equally deducible from observation, that particular flavours and odours are naturally acceptable, or the reverse, to children. And again, with reference to the sense of touch, smooth surfaces almost universally give a pleasing impression, which is not imparted by rugged surfaces. Why, then, may it not be the same with respect to the sense of sight, in the case either of colour or of form?"

It

In dwelling still further on the element of light, the inquiry naturally arises, What is it? And this, it must be replied, is a question which cannot be fully answered. It was supposed by Newton, and most of his immediate successors, that light is a material substance,

NEWTON'S THEORY OF LIGHT.

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consisting of particles emitted by luminous bodies, and moving through space with a velocity of 192,000 miles in a second.

Another theory is now generally adopted. According to this, an exceedingly thin and elastic medium, called ether, is supposed to fill all space, and to occupy the intervals between the particles of all material bodies. The particles of this ether, like those of air, are capable of being put into a state of vibration by the particles of luminous bodies which are constantly agitated; and when any of these vibrations or undulations, as they are frequently called, are conveyed through the ether to the nerves of the retina, they are said to excite the sensation of light, just as the sensation of sound is excited in the nerves of the ear by the vibrations of the air. The analogy between them is strikingly shown by a very curious experiment mentioned by Sir D. Brewster. If two equal and similar strings perform exactly 100 vibrations in a second, they will produce each equal waves of sound, and these waves will conspire to produce an uninterrupted sound, double of either of the sounds heard separately. If the two strings are not in unison, but nearly so, as in the case where the one vibrates 100 and the other 101 times in a second, then at the first vibration the two sounds will