REMARKABLE FORCE OF DIFFUSION. 



217 



entirely disappeared. As there is but one way 

 of escape through the neck, and even this pas- 

 sage is, apparently, very accurately closed, it is 

 evident, whatever the power, it was sufficient to 

 enable this naturally heavy gas to rise up and 

 leave the vessel, and the natu- 

 rally lighter air has descended 

 and filled it. A pleasing way 

 of performing this experiment 

 is to fill one jar with the light- 

 est of all known gases, hydro- 

 gen, and another with the heavy 

 carbonic acid gas, and to con- 

 nect them by two perforated 

 corks and an intervening tube, 

 as represented, and then to 

 place them in the position 

 shown, that containing the hydrogen being 

 uppermost. In a little while the heavy carbonic 

 acid gas will rise to the top of the upper jar, 

 and the light hydrogen will descend, and sink 

 into the lowest jar, until the two jars contain 

 a uniform mixture of both gases. The force 

 which produces this remarkable phenomenon is 

 the diffusive power of gases, the beautiful laws 

 of which were discovered and developed by the 

 eminent chemist, Professor T. Graham. By 

 virtue of this remarkable force, the heaviest 

 gases rise up into the air, though less rapidly 



