170 MOLECULAR ATTRACTIONS 



constituent elements of oxygen and hydrogen in 

 separate gaseous states, as by a voltameter, repre- 

 sented in Fig. 60, the oxygen molecules, rising 

 from one end, or pole of the battery circuit, ascend 

 into the inverted glass-tube o, and the hydrogen 

 into the other tube, H. The respective volumes are 

 indicated by the unshaded portions of the tubes, 

 and may be severally weighed. In this way the 

 relative weights and volumes of the oxygen and 

 hydrogen are ascertained. The molecules of 

 hydrogen occupy double the space of the mole- 

 cules of oxygen, and have only one-eighth the 

 weight. 



If the two separated gases be commingled in 

 one tube, and an electric spark be passed through 

 them, they become electro-magnetically reunited, 

 and reproduce water; which weighs as much as 

 the two separate gases. " Tested by the battery 

 poles, substances, considered singly, are neither 

 positive nor negative." 



By rendering the molecules of various com- 

 pound substances freely movable in a liquid state, 

 and placing therein the ends of a conducting-wire 

 connected with a voltaic battery, it is found that 

 one kind of molecules goes to a particular end, or 

 pole, of the battery circuit, and the other kind of 

 molecules to the opposite pole, in a systematic 

 order; commencing with molecules of oxygen, 

 which stands at the head of the list in affinity for 

 the positive pole, being electro-negative to all 



