Page:Scott's Last Expedition, Volume 1.djvu/570

372 southern temperatures at given latitudes. So far as these tables go they show the South Polar summer to be 15° colder than the North Polar, but the South Polar winter 3° warmer than the North Polar, but of course this last figure would be completely altered if the observer were to winter on the Barrier. I fancy Amundsen will not concede those 3°!!

From temperatures our lecturer turned to pressures and the upward turn of the gradient in high southern latitudes, as shown by the Discovery Expedition. This bears of course on the theory which places an anticyclone in the South Polar region. Lockyer's theories came under discussion; a good many facts appear to support them. The westerly winds of the Roaring Forties are generally understood to be a succession of cyclones. Lockyer's hypothesis supposes that there are some eight or ten cyclones continually revolving at a rate of about 10° of longitude a day, and he imagines them to extend from the 40th parallel to beyond the 60th, thus giving the strong westerly winds in the forties and easterly and southerly in 60° to 70°. Beyond 70° there appears to be generally an irregular outpouring of cold air from the Polar area, with an easterly component significant of anticyclone conditions.

Simpson evolved a new blizzard theory on this. He supposes the surface air intensely cooled over the continental and Barrier areas, and the edge of this cold region lapped by warmer air from the southern limits of Lockyer's cyclones. This would produce a condition of unstable equilibrium, with great potentiality for movement. Since,