ON THE PROGRESS OF SCIENCE. XI 



then, would be dry air ; descending into the valleys, and coming under 

 the barometric pressure at the surface, it would be warm air. Leslie 

 has explained how, by bringing the attenuated air down from the snow 

 line, even of the tropics, and subjecting it to the barometric weight of 

 the superincumbent mass, we may raise its temperature to inter-tropi- 

 cal heat by the mere pressure. In like manner this Antarctic air, 

 though cold and rare while crossing the ' barrier,' yet receiving heat 

 from its vapors as they are condensed, passing over into the valleys 

 beyond, and being again subjected to normal pressure, may become 

 warm. We have abundant illustrations of the modifying influences 

 upon climate which winds exercise after having passed mountains and 

 precipitated their vapor. The winds which drop the waters of the 

 Columbia river, etc., on the western slopes of the Rocky Mountains, 

 make a warm climate about their base on this side, so much so that 

 we find in Nebraska the lizards and reptiles of Northern Texas. 

 Indeed trappers tell me that the Upper Missouri is open in fall long 

 after the Lower is frozen up, and in spring long before several 

 weeks the ice in the more southern parts has broken up. The 

 eastern slopes of Patagonia afford even a more striking illustration of 

 climates being tempered by winds that descend from the mountains 

 bearing with them the heat that their vapor has set free. Thus you 

 observe that an exploring party after passing the barrier might, as they 

 approach the pole, find the Antarctic climate to grow milder instead 

 of colder. It would be rash in the present state of our information 

 to assert that such is the case ; but that such may be the case should 

 not be ignored by the projectors and leaders of any new expedition 

 to those regions. The existence of an open sea in the Arctic Ocean 

 has, with a great degree of probability, been theoretically established. 

 But the circumstances, as strong as they are, which favor the existence 

 of an open water there, are not so strong and direct as are the proofs 

 and indications of a mild polar climate in the Antarctic regions. I 

 have examined the immense library of lo^-books here for the lines of 



/ r> 



Antarctic ice-drift. There appear to be two, both setting to the north- 

 east, one passing by the Falkland Islands, the other having its north- 

 ern terminus in the regions about the Cape of Good Hope. Further 

 south, icebergs are found all around ; but in these lines of drift they 

 are found nearest the equator. The space between the Falkland 

 drift and the Good Hope drift is an unfrequented part of the ocean. 

 It may, therefore, be one broad drift, the edges of which only I have 

 pointed out. The most active currents from the south do not run 

 with this ice. Humboldt's current is the most active, but it does not 

 get its icebergs as far north as they come by these lines. This cir- 

 cumstance has suggested the conjecture that one part of the Antarctic 

 Continent must be peculiarly well situated for the formation of gla- 

 ciers and the launching of icebergs. These lines of drift point to 

 such a place." 



