APPLICATIONS OF THE MICROSCOPE. 137 



the channels through which the air of the trade 

 winds, after ascending at the equator, returns 

 whence it came." 



The air is invisible, and even if it could be 

 seen and seized, where is to be found the tally 

 that is to be attached to the air ? and supposing 

 it to be found, how is it to be placed upon the 

 wings of the wind ? The task seems hopeless, 

 and the very expectation utterly Utopian. But 

 it has actually been done. The Footprints of 

 the Wind may be traced through the region of 

 the clouds. " Ehrenberg, with his Microscope, 

 has established, almost beyond a doubt, that the 

 air which the south-east trade-winds bring to 

 the equator, does rise up there and pass over 

 into the northern hemisphere." 1 " The Micro- 

 scope, under the eye of Ehrenberg, has enabled 

 us to put tallies on the wings of the wind, to 

 learn of them something concerning its cir- 

 cuits." 2 



11. It occurred to Mr. Maury, that as Infu- 

 soria are found in sea-dust, rain-drops, hail- 

 stones, and snow-flakes, it might be possible to 

 ascertain from what localities these organisms 



1 Physical Geog. of the Sea, p. 117. * Ibid. p. 260. 



