628 



W, work of one pound of steam. 



% expenditure of heat per pound of steam in foot-pounds. 



0= 1 109550 foot-pounds. 



= 540'4 foot-pounds per degree Fahrenheit. 



Efficiency of steam, W---&. 



Exact Formula. 



W 



hyp. log -b^- 



l 



Approximate Formulae. 



_1Z 

 -16r *- 



In applying the exact formulae, the relations between p, v, and t 

 may be found by means of known formulae or Tables. 



February 3, 1859. 



Sir BENJAMIN C. BRODIE, Bart., President, in the Chair. 

 The following communications were read : 



I. " On Platinized Graphite Batteries." By C. V. WALKER, 

 Esq., F.R.S., F.R.A.S., & c . Received January 4, 1859. 



In a short note communicated to the Royal Society on March 

 9th, 1857, and which was read on March 19th, reference was made 

 to the voltaic combination that I had adopted for certain telegraphic 

 purposes ; namely, zinc- graphite. Graphite in its crude state had 

 for some years been of great service to me, especially for batteries 

 whose resting time is great in proportion to their working time. 

 Since the date of that notice, I have considerably increased the value 

 of graphite for electrical purposes by platinizing it according to the 

 process first described by Mr. Smee, whose platinized silver battery 

 has been long known and much used. The material to which I 

 refer by the term " Graphite/' is the crust or corrosion that is col- 

 lected from the interior of iron gas retorts that have been long in use. 



