SCIENTIFIC BALLOONING. 313 



Gaston Tissandier, use almost the same expression in describing " a 

 warm river which flowed for a whole month over the clouds." 



We may thus draw an outline sketch of the movements of the great 

 atmospheric ocean, its tides, its streams, and torrents, but a just 

 examination into its constitution goes further than the consideration 

 of temperatures and currents. Fully as important as either is the 

 question of humidity, while no records with which the aeronaut has 

 had to deal are more curious or more instructive than those that come 

 under this head. 



Going back to the times which witnessed the early exploits previ- 

 ously mentioned, we find Mr. Monck-Mason formulating a theory 

 that when rain falls and sky is overcast there will be further cloud 

 layers above, while on the contrary, when no rain falls and the sky 

 is overcast, there will be blue sky above. Thirty years later Mr. 

 Glaisher records an ascent which, while lending confirmation to this 

 theory, supplies other noteworthy observations. It had been a calm, 

 brilliant, and promising June morning till noon, when, in a manner 

 common enough in our summers, clouds had suddenly blown up and 

 darkened the sky so forbiddingly that a very hasty departure was 

 made, and, with great lifting power, his balloon rose 4,000 feet in four 

 minutes. Passing through a cold, damp cloud at that height, he found, 

 contrary to his expectations, farther clouds above, and at 9,000 feet 

 the air was full of the sighing of the wind that presages storm. At 

 that point, however, the sun shone momentarily, encouraging the 

 belief that clouds would soon be passed. But instead of this the 

 balloon again ascended into fog mingled with fine rain. The experi- 

 enced aeronaut and meteorologist now seems to have become fairly 

 astounded .at his results. At 12,000 feet he entered a wet fog, grow- 

 ing drier at 15,000 feet; then the sun peeped out, and then again 

 came wet fog. A thousand feet higher the fog was dry. A thousand 

 feet higher yet the sun once more gleamed for a moment, and then 

 gave place to fog, growing wetter, but soon passed. At 20,000 feet 

 dense clouds were still overhead, fringed and watery, while but a 

 little higher patches of blue sky appeared with floating cirrus far 

 above. 



Contrasting with this may be recorded the register obtained during 

 the late exceptional summer by the writer in a series of ascents in 

 afternoon and night hours from the Crystal Palace, from Newbury, 

 and from Clifton, which showed consistently an almost uniformly dry 

 and thirsty condition of the atmosphere up to the highest altitude 

 reached; and where clouds were met with they were fast thinning 

 away. Wandering cloudlets would wend along and vanish into air, 

 like the steam of a passing train. There was, however, one notable 

 exception during an evening in mid-September, when, traversing 

 Somersetshire at an elevation of 3,000 feet and upward, the air, 

 though remaining clear as before, had become saturated with a 



