of the Heat of Combustion. 107 



gaseous state ; whilst in the other, the hydrogen, by combining 

 with free and condensed oxygen, did not escape. Now we 

 shall see from the following experiments that electric intensity 

 is expended in the act of converting a body into the gaseous 

 state. 



39. I took ten glass jars (see fig. 3), made them perfectly 

 clean and dry*, and placed them in series on a non-conducting 

 substance. Into these I poured a quantity of dilute sulphuric 

 acid, taking care not to wet the glass within an inch of the top 

 of each. Pairs of platinized silver and amalgamated zinc were 

 placed in the jars, and connexions, furnished with the mercury 

 cups 1, 2, 3, &c., were established between them seriatim. A 

 decomposing cell, d, furnished with platinum wires, was con- 

 nected on one hand v/ith the battery, and on the other with the 

 galvanometer (5.). Lastly, 1 provided a copper wire, w, by 

 means of which connexion could be conveniently made be- 

 tween the galvanometer g, and any of the mercury cups, 1, 

 2, 3, &c. 



40 Into d I poured a small quantity of dilute sulphuric acid. 

 Then, by placing the wire w in each of the mercury cups, be- 

 ginning at 10 and ending at 10, I observed the deviations of 

 the galvanometer contained in the following table. 



41. Now if we divide the straight line, A B, fig. 4, into ten 

 equal parts, representing pairs on Mr. Smee's plan, and if at 

 each division we erect sti'aight lines, perpendicular to A B 

 and proportional to the comparative (juantities of electricity 

 just given, the principles of electric action demand that the 

 line drawn through tlie extremities oi those perpendiculars 



* It is necessary to be very careful in insulatinpr the apparatus, in order 

 to obtain the ma.vimiiiii intensity of a battery. 'I'he divided porcehiin trough 

 has frequently great conducting powers (particularly when the jjlaze has 

 been partially destroyed), which render it unfit for accurate experiments. 



