TCD MS 10516 folio 82 recto
[12th October 1916] clouds of dust that it sweeps southward before it. At evening the sun, gleaming through the dust like a metallic silver disc, is tempered by the fine sand suspended in the atmosphere; even at an angle of 15° above the horizon, the rays of heat and light are so completely screened that no direct warmth is felt, nor is the faintest shadow thrown upon the earth.
That dust should rise in the atmosphere to so great an altitude is not due, as might first be suspected, to the impetuous wind whirling the sand from lower to higher strata of the air. The wind can drive it onward; it cannot raise it upward. What occurs is, I think, this. The wind stirs the dust from the surface and drives it forward, but it is the ascending convection currents, generated by the contact of air with the