174 Dr. Faraday's Experimental Researches in Electricity. 



and has the form of a small retort containing the two elec- 

 trodes: the neck is narrow, and sufficiently long to deliver gas 

 issuing from it into a jar placed in a small pneumatic trough. 

 The electrode chamber, sealed hermetically at the part held 

 in the stand, is five inches in length, and 0*6 of an inch in 

 diameter; the neck about nine inches in length, and 0*4 of an 

 inch in diameter internally. The figure will fully indicate the 

 construction. 



712. It can hardly be requisite to remark, that in the ar- 

 rangement of any of these forms of apparatus, they, and the 

 wires connecting them with the substance, which is collaterally 

 subjected to the action of the same electric current, should be 

 so far insulated as to ensure a certainty that all the electri- 

 city which passes through the one shall also be transmitted 

 through the other. 



713. Next to the precaution of collecting the gases, if min- 

 gled, out of contact with the platinum, was the necessity of 

 testing the law of a definite electrolytic action, upon water at 

 least, under all varieties of condition; that, with a conviction 

 of its certainty, might also be obtained a knowledge of those 

 interfering circumstances which would require to be practi- 

 cally guarded against. 



714. The first point investigated was the influence or in- 

 difference of extensive variations in the size of the electrodes, 

 for which purpose instruments like those last described (709. 

 710. 711.) were used. One of these had plates 0*7 of an inch 

 wide, and nearly four inches long; another had plates only 

 0*5 of an inch wide, and 0*8 of an inch long; a third had 

 wires 0*02 of an inch in diameter, and three inches long; and 

 a fourth similar wires only half an inch in length. Yet when 

 these were filled with dilute sulphuric acid, and, being placed 

 in succession, had one common current of electricity passed 

 through them, very nearly the same quantity of gas was 

 evolved in all. The difference was sometimes in favour of 

 one, and sometimes on the side of another ; but the general 

 result was that the largest quantity of gases was evolved upon 

 the smallersurface of the wires. 



715. Experiments of a similar kind were made with the 

 single-plate, straight tubes (707.) , and also with the curved 

 tubes (70S.), with similar consequences; and when these, with 

 the former tubes, were arranged together in various ways, the 

 result, as to the equality of action of large and small metallic 

 surfaces when delivering and receiving the same current of 

 electricity, was constantly the same. As an illustration, the 

 following numbers are given. An instrument with two wires 

 evolved 74*3 volumes of mixed gases ; another with plates 



