Decomposition and Recomposition of Water. 337 



iron cap, in which a female screw is wrought so as to allow a 

 large iron valve cock (C) to be screwed to it. 



Upon the tabulures also iron caps are cemented, which are so 

 wrought as, with the aid of appropriate screws, to constitute stuff- 

 ing boxes. 



Through each of these a platina rod (D, d) is introduced, and 

 fastened to plates of platina, to act as " electrodes,^'' agreeably to 

 the language of the celebrated Faraday. 



The tube being supported over the mercurial cistern, by means 

 of a communication with an air pump, through the valve cock 

 and flexible leaden pipe, the bore of the tube is exhausted of air, 

 so as to cause the mercury to take its place. 



The mercury is so far displaced by a solution of borax, con- 

 sisting of equal parts of water and saturated solution of that salt, 

 as to sink the surface of the column of metal in the tube about 

 an inch or more below the "electrodes." The projecting end of 

 one of the rods (D, d,) to the other ends of which the " electrodes" 

 are severally attached, is bent at right angles outside of the tube, 

 so as to enter some mercury in an iron capsule, supported purposely 

 at a proper height, and communicating with one end of my defla- 

 grator of an hundred pairs of Cruickshank plates of about eight 

 inches by foureteen. Of course the rod of the other electrode 

 must have a communication with the other end of the deflagrator. 

 Under these circumstances, if the circuit be completed by throw- 

 ing the acid on the plates of the deflagrator, a most rapid evolu- 

 tion of hydrogen and oxygen will ensue in consequence of the 

 decomposition of the water, so that within a few seconds, several 

 cubic inches of gas will be collected. 



The action being now suspended by throwing the acid off the 

 plates, and the foam being allowed to subside, the resulting gase- 

 ous mixture may be ignited, and of course condensed, by com- 

 pleting the circuit again as at first, and at the same time causing 

 the ends of the " electrodes" to come into contact with each other, 

 and thus to produce a spark. 



This contact is effected by causing a very slight movement in 

 the rod, bent at right angles, and entering the mercury in the 

 iron capsule. Of course the process may be repeated as often as 

 can be reasonably desired. 



Vol. XXXVIII, No. 2.— Jan.-March, 1840. 43 



