280 Mr. H. F. Morley en Grove's Gas-Battery. 



In one case the oxygen-wire gave a negative deflection of 

 about 1. 



I found that when I ignited a platinum wire in a Bunsen's 

 flame it acquired a positive potential of about 20, as if it had 

 absorbed oxygen. In §§ IX., X., and XL the cell was com- 

 posed of a couple of test-tubes inverted in a beaker of acid, 

 and the wires were introduced by pushing them through a 

 couple of narrow U-tubes, the shorter arms of which were 

 inside the test-tubes. This arrangement made it very easy to 

 change the wires. 



XII. The maximum polarization of a voltameter is scarcely, 

 if at all, altered by diminution of pressure (Crova) ; and the 

 same seems to hold for increased pressure. So also is the 

 electromotive force of a freshly charged gas-couple — being, in 

 fact, little less than that maximum polarization. I connected 

 the terminals of a gas-couple with a condenser which could be 

 discharged through a galvanometer ; I then developed gas by 

 electrolysis for a few minutes, during which time the difference 

 of potential between the wires, which I will call E, was 189, 

 the pressure being 77 centims. of mercury ; the battery was 

 then cut out, and as soon as most of the bubbles, except those 

 sticking to the wires, had risen, I found E = 60. The wires 

 were now short-circuited until E = 34, when the pressure was 

 increased to 145 centims., after which the battery was put on and 

 E = 191 ; then the battery was cut out as before, and E = 62; 

 then the wires were short-circuited till E = 37 ; then the 

 pressure was reduced to 22 centims. ; then the battery was 

 put on, and E = 200; after cutting out the battery, E = 60. 

 The initial electromotive force of the element is not aifected 

 by the length of time the battery is in circuit. 



The difference of potential between the terminals of the bat- 

 tery was about 260, but was slowly rising during the experi- 

 ment. When hydrogen is liberated from the surface of the 

 wire, the platinum attracts as much of it as it can : this 

 quantity seems not to vary with the pressure ; I do not 

 know why it should so vary ; and it determines the maximum 

 polarization. The slight increase of the polarization with 

 pressure may perhaps be attributed to changes in the density 

 of the oxygen. 



XIII. A gas-couple charged with chemically prepared oxygen 

 and hydrogen was short-circuited through a galvanometer of 123 

 ohms resistance, and subjected to various pressures, the top of 

 the wire in hydrogen being 5*7 centims. below the surface of the 

 liquid in its tube, and that of the wire in oxygen being 5*4 

 centims. below the surface. At a pressure of 76 centims., 

 deflection 15. At a pressure of 144 centims. the deflection 



