110 TRANSACTIONS OF THE ILLINOIS 



Observations made in all parts of the globe have established the 

 fact that there are three species of both high and low barometers ; namelv, 

 permanent, periodical and temporary. There are four permanent high 

 barometers, located as follows : One in the North Atlantic, one in the 

 South Atlantic, one in the South Pacific, and one in the North Pacific. 

 To these may be added a fifth, a comparative high barometer in summer, 

 of small dimensions, over Hudson's Bay. The oceanic high barometers 

 swing considerably north and south, keeping within limits their relative 

 position to the declination of the sun, and they are continually oscillating 

 from east to west ; for instance, that in the North Atlantic encroaches 

 considerably at times upon the eastern portion of the American continent, 

 and upon the western portions of both Europe and Africa. 



The permanent low barometers are five, located as follows : One 

 around each pole of the earth, one on the equator, extending entirely 

 around the globe, one over Iceland and southeastern Greenland, and 

 one in the North Pacific ocean, covering tfie Aleutian Archipelago. It 

 will thus be perceived that there are no high nor low permanent barome- 

 ters excepting over the oceans. Continents give rise to the phenomena 

 of periodical high and low barometers. They are called periodical, be- 

 cause in the winters of both hemispheres a high barometer occupies the 

 centers of continents ; and in their summers a low barometer prevails 

 at those centers. That is, the periodical high and low barometers 

 change places when the sun crosses the equator. Hence, in the interior 

 of Asia, and north of the 45th parallel of north latitude, there is a low 

 barometer in summer and a high one in winter; a low barometer central 

 in the valley of the Sasgatchawan, in Monitoba, North America; and 

 one in South Africa, from October to March — the summer months of the 

 Southern Hemisphere. The one in South America is not so distinctly 

 marked, on account of the narrowness of the continent there. The per- 

 manent high barometers have their centers or maximum pressure in both 

 hemispheres between the 35 th and 40th parallel. Their centers generally 

 are marked by Sargasso seas ; and their out-blowing winds cause that 

 whirl in the oceans which gives rise to the great equatorial current, the 

 gulf-stream on the east coast of North America, the Kuro Sivo on the 

 east coast of Asia, and to the northern currents along the west coasts of 

 both Europe and North America. The currents along the coasts of the 

 southern continents obey the same law, but, as a matter of course, their 

 directions are reversed, since the action of the motive force is reversed. 



The average pressure of both permanent and periodical high barome- 

 ters, at their centers, is 30.3 inches, excepting that of Hudson's Bay, which 

 is about 30 inches. The average pressure of the low barometers, both 

 permanent and periodical, is as follows: Equatorial, 29.9 inches; Ice- 

 land, 29.5 inches; Aleutian, 29.6 inches; Polar, unknown, probably 29.4 

 inches; North America, 29.6 inches; Asiatic, 29.5 inches, and South 

 Africa, 29.6 inches. Periodical barometers disintegrate, and send off 

 temporary high and low barometers, which, if not controlled in their 

 movements by their opposites, take a direct course to the nearest similar 

 permanent barometer; that is, a temporary low barometer to a permanent 

 low one, and vice versa. The disintegrated parts of low, or temporary 



