in that thin, bracing air, that we had wriggled to the surface like the larvae of mosquitoes, and, after incessantly gyrating up and down, had crawled clear and grown our wings in the drier medium. But even while thinking these things the sun slipped down behind the opposite hills, the mist thickened, a cold draught sucked around the side of the mountain, and I heard Vinckers let out his breath with a shudder. I had noticed that each evening we grew depressed as soon as the sun was gone.
"'What is the matter?' I asked.
" 'Oh, God!' he shuddered. 'Don't you see that it is all getting yellow again—a nasty, greenish yellow?'
"'Ou aye,' said MacFarlane, 'but it has been yellow all day!'
"It had a yellowish tinge to me, Doctor, but I had tried to persuade myself that it was something in the spectrum of that equatorial sun and the vivid greens which filled the valley. There was no denying that as the sun-
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