The sun still flamed in the heavens when, shortly before noon, Jack and I brought our sextants on deck with the object of measuring his meridian altitude above the horizon; but we were only able to obtain a very approximate and wholly useless result, for, when we came to try, we found that the sun appeared in our instruments merely as a shapeless glare of light, while the horizon was wholly indistinguishable.  Then, by imperceptible degrees, the sun, like the horizon, became obliterated, and the atmosphere stealthily darkened, as though a continuous succession of curtains of grey gauze were being interposed between us and the sky.  Meanwhile the barometer was still persistently declining, although not quite so rapidly as during the early hours of the morning.