ON A NEW STEAM-POWER METER. 151 



and those coasts placed generally in the same position with regard to know- 

 ledge of the tides as those of England. The same may be said of the ports of 

 Australia, China, &c., as well as of western America. 



78. But while admitting the practical sufficiency of Mr. Parkes's analysis 

 for the purpose of establishing processes for the computation of tide-tables, the 

 Committee believe the further application of the harmonic system to be very 

 desirable, from its more searching character and the facility with which it 

 exhibits the smaller variations of level independently of theory. 



79. Whether it will, for practical purposes, supersede existing methods of 

 prediction, wiU probably depend upon the relative amoimt of labour re- 

 quired for the calculations ; but there is little doubt that it will at any rate 

 facilitate the correction of existing formulae. 



SO. For more strictly scientific purposes its superiority to any existing 

 method of analysis is indisputable, and, considering the relation of tidal 

 variations to many physical questions at present unsolved, its importance 

 from this point of view is great. 



81. It may fairly be expected that the Admiralty will cooperate in carry- 

 ing on a work which, whether in its scientific or practical bearings, is of 

 such fundamental importance for navigation. 



On a new Steam-power Meier. By Messrs. Ashton a7id Storey. 



[A communication ordered to be printed in extenso in the Transactions.] 



Tee extent to which the employment of steam-power in our varied in- 

 dustries, and as furnishing means of locomotion, has become a necessity, 

 and the desirability of attaining the utmost economy in the consumption 

 of fuel, render it a matter of the first importance to be able readUy to ascer- 

 tain the exact amount of power developed by steam machinery in a given 

 time. Hitherto approximate estimates, founded upon the results of iso- 

 lated tests and experiments, or calculations based upon the diagrams pro- 

 duced by ordinary indicators, have furnished the sole means for the ascer- 

 tainment of the duty of (or, in other words, the power developed by) steam- 

 engines in all cases where the said power has been subject to variations. 



These indications have been taken at intervals of at least one day, and 

 in most cases of a much longer period, and have simply been registrations 

 of the amount of power developed during the one stroke or the two or 

 three strokes performed by the engine during the time of indication, the 

 great variations in the load upon or the speed of the engine, and in the 

 pressure of the steam, occurring in the intervals between the indications 

 being practically disregarded ; and even when a correct diagram has been 

 obtained, the power developed during the indication has and can only be 

 ascertained with any degree of exactness by a tedious process of mea- 

 surement and calculation. The patent power-meter and continuous indi- 

 cator, on the contrary, not only measures the power developed during a 

 single stroke of the engine with as great a degree of exactness as the best 

 indicator hitherto in use, but also registers the result of the said measure- 

 ment with as great a degree of exactness as it is measured, thus avoiding 

 the errors arising in the operation of measuring and calculating the area 

 of the ordinary diagram ; and, what is of more consequence, this measure- 



