Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 1.djvu/79

] As opportunities offered, experiments were made to determine the height of the plane of vapour, a desideratum of great meteorological importance, connected with all the most interesting questions regarding the distribution of aqueous vapour over the globe and the irrigation of the continents. The results of these experiments differed so widely from each other, owing chiefly to the great difficulty of any thing like exact determination in observations of this nature, and probably in some degree from an actual difference of its altitude, under various conditions of the atmosphere, ranging from one thousand two hundred to nearly three thousand feet, barely entitle them to be esteemed more than a rough approximation, giving an elevation of about two thousand feet as its mean height in the tropical regions.

On the 27th, the sky being very clear, the planet Venus was seen near the zenith, notwithstanding the brightness of the meridian sun, and was an object of much admiration to us all. It enabled us to observe the higher stratum of clouds to be moving in an exactly opposite direction to that of the wind, a circumstance which is frequently recorded in our meteorological journal, both in the N.E. and S.E. trades, and has also been observed by former voyagers. Captain Basil Hall witnessed it from the summit of the Peak of Teneriffe; and Count Strzelecki, on ascending the volcanic mountain of Kirauea, in Owhyhee, reached, at 4,000 feet, an elevation above that of the trade wind, and