THE 

 LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



SUPPLEMENT to VOL. XIV. THIRD SERIES. 



LXXI. 0)1 the Expansive Action of Steam in some of the Pump- 

 ing Engines on the Cornish Mines. By William .Tout 

 Hen WOOD, F.G.S., Secretary of the Royal Geological Society 

 of Cornwall, H. M. Assay-Master of Tin in the Duchy of 

 Coriiisoall* . 



'T'HE experiments which it is my purpose to describe, were 

 -■- instituted with a view to the determination of the quan- 

 tity of steam employed, and the mode of its distribution on 

 the working stroke; the duty performed with a given quan- 

 tity of fuel ; and the work accomplished for a certain expense. 



L The quantity of steam employed, and the mode of its dis- 

 tribution on the "working stroke, were approximated to by the 

 use of an indicator, lent me for the purpose by Robert Were 

 Fox, Esq. It consists of a brass cylinder about 11 inches 

 long, and 1*6 inch in diameter, open at both ends, and accu- 

 rately fitted with a piston, which, when at rest, is retained 

 near the middle of the cylinder by a spiral spring, of which 

 one end is attached to the piston, and the other to the top of 

 the cylinder: the upper extremity of the piston-rod is pro- 

 vided witli a receptacle for a pencil. A tapered stop-cock is 

 fixed on the lower end of the cylinder, and is introduced into 

 the grease-hole or other aperture in the cylinder-cover of any 

 engine on which the indicator is placed. A light frame of 

 wood, about IS inches long and 4 inches wide, is fastened to 

 the top of the indicator-cylinder, and in it a small board slides 

 horizontally in grooves. 



During the working stroke of the engine a direct motion 

 is given to the slider by means of a string which passes over 

 a })ulley, and is connected with the radius-rod of the parallel 

 motion. Its return is effected by the action of a counterpoise 

 suspended over a similar small wheel. 0)i this moveable 

 board a piece of paper is firmly secured, and a pencil is placed 

 on the top of the piston-rod of the indicator. 



* The 'J'clford Medal of the Institution of Civil Engineers was awanled 

 to this communication, which appears in the second voliune of their 

 Transactions. 



Phil, Mag, S. 3. Vol. W, No. 92. Suppl.July, 1839. 2 1 



