174 THE CHEMISTRY OF CREATION. 



the rest of the heavenly bodies, so that we who 

 " would pass from hence to them, cannot ;" but 

 whether other beings from them to us may pass 

 or not, cannot be so clearly demonstrated. 



It is one of the curious and interesting dis- 

 coveries of modern meteorology, that the airy 

 ocean is agitated like that of water by tides. 

 These are, apparently, of two kinds, the first 

 being the result of the heat of the sun's rays, 

 the second being due to the attraction of the 

 moon. The atmosphere is heated, to some 

 extent, by the transmission of the heat-rays from 

 the sun through it, but chiefly by contact with 

 the earth heated by the sun. Air, when heated, 

 expands, and becomes lighter, and consequently 

 rises ; by this law the occurrence of the aerial 

 tides is easily and simply explicable. It is 

 perhaps necessary to mention, that the manner 

 in which the fact is observed, is by carefully 

 noting, at different periods of the day, the 

 height at which the mercurial column stands in 

 the barometer tube. Between the tropics, the ebb 

 and flow, as it might be expected, of the atmo- 

 sphere, is one of the most remarkable natural 

 phenomena. The periodic rise and fall of the 

 barometer in these regions is, in fact, due to 

 the ebb and flow of the atmospheric tides. The 

 variations occur daily in the following order, 

 according to Humboldt : Twice a day the baro- 



