312 SCIENTIFIC BALLOONING. 



Leaving the earth at 9.30, the temperature rose rapidly up to 500 feet, 

 at which elevation a colder stratum was encountered. In another hun- 

 dred feet warmer air was again met with, after which a second and a 

 third cold stratum was found and passed, beyond which the air grew 

 sensibly warmer, reaching 50° at 6,000 feet, that is, some 15° higher, 

 probably, than the earth temperature at that moment. 



The question, then, here arises, Do warmer layers exist above as 

 true strata, or are there rather, floating aloft and all unseen, detached 

 masses of a warmer air, which, if visible, would resemble a mottled, or 

 patchy, or stratified sky 1 ? This point will be discussed later in relation 

 to certain phenomena of sound. 



It is clear, however, that though the diurnal rise and fall — the 

 vertical ebb and flow, as it were — of atmospheric currents near the 

 earth's surface is a most important factor demanding thorough exami- 

 nation, it is yet more needful to trace, by all means available, the 

 vaster and more general lateral sweeps of the ocean depths above. 

 Valuable information respecting such winds as play over a large con- 

 tinent has been gathered from systematic observations made with high 

 flying kites in America, where confirming those views of aeronauts 

 already mentioned, it has been found that at considerable elevations 

 the kites have usually encountered winds blowing from the west while 

 a daily rotation of shallower winds prevails below. A remarkable 

 characteristic, moreover, met with is that where the direction of such 

 winds changes, the change may be perfectly abrupt. It has, indeed, 

 been recorded by scientific balloonists that they find, in the regions 

 where winds of different directions pass, that one appears actually to 

 drag against the surface of the other, as though tolerating no interval 

 of calm or transition; and yet a more striking fact is that a very 

 hurricane may brood over a placid atmosphere with a clean-cut surface 

 of demarcation between calm and storm. 



Mr. Whymper, watching an eruption of Cotopaxi from a station 60 

 miles distant^ observed a violent uprush of inky vapor ascend quite 

 vertically through serene air till, as he judged, it had reached an 

 altitude of 20,000 feet above the crater, or twice that height above sea 

 level. At that point it "encountered a powerful wind blowing from 

 the east, and was rapidly borne toward the Pacific, seeming to spread 

 very slightly, and presenting the appearance of a gigantic i— drawn 

 upon an otherwise perfectly clear sky. It was then caught by wind 

 from the north, and, borne toward him, appeared to spread quickly." 



It is not only, however, when winds cross at different heights that 

 this remarkable close restraint within their own limits is to be noticed. 

 Even on the same level contrary winds will maintain their distinctive 

 flow more determinedly than cross currents of water amid stream. 

 Thus, Mr. Charles Darwin found on mountain heights winds turbulent 

 and uncon fined, yet holding their courses like "rivers within their 

 beds;" so again the French aeronauts, MM. W. de Fonvielle and 



