Page:Physical Geography of the Sea and its Meteorology.djvu/481

Rh in the ice there. The annals of Greenwich at St. Petersburg give us the mean height of the barometer in lat. 51° 29' N., according to three years' observations, and in lat. 59° 51' N., according to ten years of observation. Such are the sources of the table.

Mean Height of the Barometer

856. The low austral barometer.—Captain Wilkes, U. S. N., and Clarke Ross, R.N., both, during their expeditions to the South Seas in 1839-41, had occasion to remark upon the apparent deficiency of atmosphere over the extra-tropical regions of the southern hemisphere; and the low barometer off Cape Horn had attracted the attention of navigators at an early day. I observed it in 1831 when doubling the Cape as master of the U.S.S. "Falmouth," and wrote a paper on it, which was published in the American Journal of Science in 1833-4. The more abundant materials which the abstract logs since placed within my reach have enabled me to go more fully into this subject than it was possible to do while I was cruising in the Pacific more than a quarter of a century ago. To ascertain whether these "barometric anomalies," as they are called, are peculiar to the regions about Cape Horn, or whether they are common to high southern latitudes in all longitudes, the observations about Cape Horn were arranged in one group; those between 20° W. and 140° E.