Note 38 — ON STEPPES AND DESERTS.
Henry G. (Henry George) Bohn translation
p. 16.—“The scene suddenly changes in the Steppe.”
I have endeavoured to describe the approach of the rainy season, and the signs by which it is announced. The deep blue of the heavens in the tropics is occasioned by the imperfect solution of vapour. The cyanometer indicates a lighter shade of blue as soon as the vapours begin to fall. The dark spot in the constellation of the Southern Cross becomes indistinct in proportion as the transparency of the atmosphere decreases, and this change announces the approach of rain. The bright radiance of the Magellanic clouds (Nubecula major and Nubecula minor) then gradually fades away. The fixed stars which had before been shining with a calm, steady, planetlike 139light, are now seen to scintillate in the zenith.[HB] All these phenomena are the result of the increased quantity of aqueous vapour floating in the atmosphere.