ON A CONSTANT INDICATOR FOR STEAM-ENGINES. 307 



Report of a Committee appointed at the Tenth Meeting of the Associa- 

 tion, on the Construction of a Constant Indicator for Steam-Engines. 

 Members of the Committee, the Rev. Professor Moseley, M.A., 

 F.R.S., Eaton Hodgkinson, Esq., F.R.S., J. Enys, Esq. 



A REGISTRATION of the work done by a steam-engine made at its piston, or 

 of the work done by the steam upon the piston, appears to offer important 

 practical advantages, as compared with any other method of registration, in 

 these respects ; that it is applicable to every possible variety in the circum- 

 stances under which the engine is made to operate, and that it is a registra- 

 tion of the work of the engine ahsolutely, and separated from all those uncer- 

 tain influences of friction, or other prejudicial I'esistances which intervene 

 between the piston and the working points of the machine to which it gives 

 motion ; influences which it is impossible to eliminate from a registration of 

 the work done at the working points, with certainty or accuracy. 



In proof of the advantages which would result from any method of regi- 

 stration of the work, and therefore of the duty of steam-engines, could it be 

 made to assume this general character, it is sufficient to point to the history 

 of the Cornish pumping-engines. It is entirely from the registration of their 

 work (so easily made in respect to them by reason of the simple and constant 

 nature of that work), that has resulted that admirable knowledge of the 

 working properties of the steam-engine, which is so extensively diff"used 

 through the mining districts ; and to the same cause is entirely due (as a 

 consequence of this knowledge), that vast economy of power and fuel in the 

 working of the Cornish engines, which has so recently been brought under 

 the consideration of the Association. 



If a method of registration equally (or even yet more) certain and easy of 

 application could be extended to the working of all engines, no matter how 

 varied or how complicated, or how intermittent the nature of their operations 

 might be — to the engines, for instance, which perform the varied and inter- 

 mittent labours of an engineer's workshop or a manufactorj^ or to the engine 

 of a steam-boat — giving by a method beyond the control or interference of 

 the engineer, the ivork of the engine of such a boat during any given time 

 — a day, a week, or a month, — and the duty which the engine does with each 

 bushel of coals, independently of her speed through the water, and of all 

 considerations dependent upon \\\eform of the boat, or the direction or force 

 of the winds or currents, or of the tides — it would at once become possible, 

 by recording and publishing the duty of each engine periodically, to intro- 

 duce precisely that competition of economy in power between the engineers 

 in factories and the engineers in steam-boats, which has been attended with 

 results of such advantage to the mining districts of Cornwall. 



If, again, we conceive the work of each of the engines of a railway com' 

 pany to be made thus to register itself, and the amount thus registered to be 

 published under the form of a weekly or a monthly return, together with the 

 quantity of the coals consumed by each, it is evident that a competition 

 amongst the engineers would be the immediate result, and a consequent 

 economy to the company in the use of the fuel. A competition which 

 would probably lead to that scientific adjustment of the amount of tlie load 

 to the evaporating power of the engine and the speed of transit, which 

 adjustment is the true and the great secret of the economical working of a 

 line of railway. Passing over the use which the resident engineer of such a 

 line of railway might make of an indicator like this, to determine the condi- 

 tion of the rails, and the general working state of any portion of the line, by 



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