The dirty little place was impenetrably black except in one spot, where he perceived an unusual glow of light.  Approaching this, he discovered it to be the crystal egg, which was standing on the corner of the counter towards the window.  A thin ray smote through a crack in the shutters, impinged upon the object, and seemed as it were to fill its entire interior.

It occurred to Mr. Cave that this was not in accordance with the laws of optics as he had known them in his younger days.  He could understand the rays being refracted by the crystal and coming to a focus in its interior, but this diffusion jarred with his physical conceptions.  He approached the crystal nearly, peering into it and round it, with a transient revival of the scientific curiosity that in his youth had determined his choice of a calling.  He was surprised to find the light not steady, but writhing within the substance of the egg, as though that object was a hollow sphere of some luminous vapour.  In moving about to get different points of view, he suddenly found that he had come between it and the ray, and that the crystal none the less remained luminous.  Greatly astonished, he lifted it out of the light ray and carried it to the darkest part of the shop.  It remained bright for some four or five minutes, when it slowly faded and went out.  He placed it in the thin streak of daylight, and its luminousness was almost immediately restored.

So far, at least, Mr. Wace was able to verify the remarkable story of Mr. Cave.  He has himself repeatedly held this crystal in a ray of light (which had to be of a less diameter than one millimetre).  And in a perfect darkness, such as could be produced by velvet wrapping, the crystal did undoubtedly appear very faintly phosphorescent.  It would seem, however, that the luminousness was of some exceptional sort, and not equally visible to all eyes; for Mr. Harbinger—­whose name will be familiar to the scientific reader in connection with the Pasteur Institute—­was quite unable to see any light whatever.  And Mr. Wace’s own capacity for its appreciation was out of comparison inferior to that of Mr. Cave’s.  Even with Mr. Cave the power varied very considerably:  his vision was most vivid during states of extreme weakness and fatigue.

Now, from the outset, this light in the crystal exercised a curious fascination upon Mr. Cave.  And it says more for his loneliness of soul than a volume of pathetic writing could do, that he told no human being of his curious observations.  He seems to have been living in such an atmosphere of petty spite that to admit the existence of a pleasure would have been to risk the loss of it.  He found that as the dawn advanced, and the amount of diffused light increased, the crystal became to all appearance non-luminous.  And for some time he was unable to see anything in it, except at night-time, in dark corners of the shop.