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The whole refracting apparatus, with its brass fittings and rings of prisms, glittered and sparkled like a domeshaped shrine of diamonds, containing not a lamp, but some sacred flame, dominating the sea. And Linda, the keeper, in black, with a pale face, drooped low in a wooden chair, alone with her jealousy, far above the shames and passions of the earth.
It is surrounded by coats, which contain refracting mediums, called humors. There are three coats, called the sclerotic, the choroid, and the retina; and three humors, called the aqueous, the crystalline, and the vitreous. The sclerotic or outer coat, called also the white of the eye, is an opaque, fibrous membrane.
We present several figures showing how these spectral images, as they are sometimes called, will appear; first, when the eye-piece is pushed in, and secondly, when it is drawn out, with telescopes of different qualities. We have thus far spoken only of the refracting telescope, because it is the kind with which an observer would naturally seek to supply himself.
The only mode, therefore, of prosecuting this inquiry is that afforded by the Method of Agreement; by which, in fact, through a comparison of all the known substances which have the property of doubly refracting light, it was ascertained that they agree in the circumstance of being crystalline substances; and though the converse does not hold, though all crystalline substances have not the property of double refraction, it was concluded, with reason, that there is a real connexion between these two properties; that either crystalline structure, or the cause which gives rise to that structure, is one of the conditions of double refraction.
Not only do natural bodies behave in this way, but it is possible, as shown by Brewster, to confer, by artificial strain or pressure, a temporary double refracting structure upon non-crystalline bodies such as common glass. This is a point worthy of illustration. When I place a bar of wood across my knee and seek to break it, what is the mechanical condition of the bar?
On either side, as of old, still rose up the towering carven stalls; the splendid pavement still shone beneath, refracting back from its surface the glimmer of light from the stained windows above; but the head of the body was gone. Somewhere, beneath the deep shadowed altar screen, they could make out an erection that might have been an altar, only they knew that it was not.
For there were others, fortunately, who did not despair of the possibilities of the refracting microscope, and their efforts were destined before long to be crowned with a degree of success not even dreamed of by any preceding generation.
Was the whole universe but a refracting speck upon some greater Being? Were our worlds but the atoms of another universe, and those again of another, and so on through an endless progression? And what was I? Was I indeed immaterial? A vague persuasion of a body gathering about me came into my suspense.
If all the rays from one point of the object, a, are to be concentrated on a corresponding point of the retina, a which would then become the exclusive representative of a, we must have one or more refracting surfaces interposed, to gather the rays together. The presence of the lens, with its various coatings, has made representation of point by point possible for the eye.
It was, I think, sometime in 1878 that I received a letter from Otto Struve, director of the Pulkova Observatory, stating that he was arranging with his government for a grant of money to build one of the largest refracting telescopes.
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