400 Scientific Intelligence — Meteorology , 



the atmospheric pressure being so very much less in the southern 

 than in the northern hemisphere, remains to be determined ; and I 

 trust that the very extensive series of observations made on board 

 the Erebus and Terror, will be of material assistance in the impor- 

 tant inquiry. — Cajptain Sir James C. Rosses Voyage to the Southern 

 Seas, during the years 1839-43, vol. ii. p. 384. 184?. 



6. Height of the plane of Vapour in the Atmosphere^ and dif- 

 ferent directions of superincumbent Streams of Air. — As oppor- 

 tunities offered, experiments were made to determine the height of 

 the plane of vapour, a desideratum of great meteorological impor- 

 tance, 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 thou- 

 sand two hundred to nearly three thousand feet, barely entitle them 

 to be esteemed more than a rough approximation, giving an eleva- 

 tion of about two thousand feet as its mean height in the tropical 

 regions. 



On the 27th November 1839, 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 exact opposite direction to that of the wind, a circumstance 

 which is frequently recorded in our Meteorological Journal, both in 

 the NE. and SE. 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 4000 feet, an eleva- 

 tion above that of the trade-wind, and experienced the influence of an 

 opposite current of air, of a different hygrometric and thermometric 

 condition ; facts which tend, in some degree, to explain the means 

 by which the equilibrium of the atmosphere, under certain condi- 

 tions, is maintained in those reorions. Count Strzelecki further in- 

 formed me of the following seemingly anomalous circumstance, — 

 that at the height of 6,000 feet he found the current of air blowing 

 at right angles to both the lower strata, also of a different hygro- 

 metric and thermometric condition, but warmer than the interstra- 

 tum. — Captain Sir James C. Bosses Voyage to the Southern Seas, 

 vol. i., p. 13. 



7. Imaginary Land. — A remarkable appearance of land was 

 reported in the evening, and, continuing for many hours without 

 any alteration of figure, several of the officers imagined it was really 

 land they saw, assuming the appearance of many pointed hills per- 



