Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 2.djvu/429

] The mean pressure and the amount of atmospheric tide in each latitude are as follows:—

The above results are arranged in belts of latitude, the observations at sea being separated from those made in harbour; this occasions more apparent irregularity than would have been the case had they been formed into two distinct tables.

It has hitherto been considered that the mean pressure of the atmosphere at the level of the sea was nearly the same in all parts of the world, as no material difference occurs between the equator and the highest northern latitudes. At Melville Island in latitude 74¾° it was found to be 29.870, at Igloolik in latitude 69°, 29.770; and at Winter Island in latitude 66° 11′, 29.798. The cause of the atmospheric pressure being so very much less in the southern than in the northern hemisphere