48 REPORT — 1860. 



sea to be remarkably accordant, that the atmosphere is much more attenuated in 

 austral than in boreal regions ; and that the high barometer, with the light airs 

 and baffling winds of the tropical calm belts, is the dividing atmospherical ridge, so 

 to speak, between the low barometer about the Pole on one side and near the Equator 

 on the other ; and that the position of this ridge is determined by the degree of 

 polar in contrast with the degree of equatorial rarefaction. The trade-winds rushing 

 in on one side, and the couuter trades on the other — as the polar- bound winds may 

 be called — supply the indraught for these places of attenuated air and low baro- 

 meter. 



It thus appears that the equatorial calm belt is a sort of thermal adjustment be- 

 tween the calms of Cancer and Capricorn ; which in turn are in adjustment to the 

 dynamical power of the ascending columns of air in the equatorial and polar calm 

 places. 



The low barometer off Cape Horn has long attracted the attention of navigators. 

 The low barometer in other longitudes south caused Wilkes, Ross, and others, to 

 remark upon the diminished pressure in high southern latitudes, and upon the ap- 

 parent inequality in the distribution of the atmosphere north and south of the 

 Equator. 



The barometric observations between 40° and 60° South, and which are quoted 

 in the preceding Table, were collected in three groups — first, from the logs between 

 the Cape of Good Hope and Australia, next from Australia to 80° West, and then 

 about Cape Horn. The result showed that a low barometer is not peculiar to Cape 

 Horn regions, but that it is general and circumferential in austral latitudes, dimi- 

 nishing rapidly as we approach the Pole. 



The great extent of the austral water surface, with the vapour with which it 

 keeps the " brave west winds" of these regions loaded, and the heat which with the 

 condensation of these vapours is liberated there, suggests the cause of this low 

 barometer. 



If it be the vapour and the liberation of its latent heat that cause the permanent 

 expulsion from Antarctic regions of so much of the atmosphere as this curve and 

 these observations indicate, then should we not follow the argument up, and infer 

 that the extreme cold of the Antarctic climate is by no means so severe as that of the 

 north ? 



The unexplored regions of the south embrace an area of more than eight million 

 square miles, or about one-sixth of the whole extent of the dry land surface that is 

 contained on our planet. 



Since the attempts to penetrate those unknown regions, steam has been intro- 

 duced upon the ocean, and the modern explorer has at his command a power which 

 enables him to defy wind and tide. Hygiene on board ship has been so improved, 

 that the sailor may now keep the sea for almost an indefinite period of time. The 

 invention, the discoveries, and the improvements of the age, place in our hands the 

 means of fitting out Antarctic expeditions, and of endowing them with powers that 

 would have made any previous expedition there doubly effective. 



Under these circumstances, would it not be a reproach upon the Christian nations, 

 and especially upon those great governments who have agreed to unite in a common 

 plan of physical research at sea, if so large a portion of the earth's surface were 

 permitted to remain unexplored ? 



Plate III. shows the furthest reach of Antarctic exploration. The tracks of Ant- 

 arctic explorers, from Cook down to the present day, go to make up these limits. 



It is not the object of this paper to elaborate the views suggested by the observations 

 offered with this paper ; but rather to present the observations themselves, with 

 such explanation as seemed necessary to enable others to understand them. 



If I have succeeded in doing this, all who will take the trouble to study them will 

 find them very suggestive. M. F. Maury. 



Observatory, Washington, 11th May, I860. 



On the Cause of the Descent of Glaciers. By the Rev. Hexry Moseley, 

 F.R.S., Canon of Bristol, Inst. Imp. Sc. Paris Corresp. 



The fact of the descent of a body, when placed upon an inclined plane, due to the 



