1S40] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



65 



In all cases I am inclined to think the pitwork resistances exceed 

 the decrease due to deficient water delivery. There are no data for 

 duty calculation, except by valueless approximations. I shall how- 

 ever submit to public opinion the following estimate of the gross power 

 of this engine, in comparison with that derived from the " Average 

 Steam Pressure, taken by indicator," in the Lancashire factory engine. 

 I conceive the allowance of half a pound per circular inch for the 

 " friction of tlie engine itself," a quantity scarcely sullicient to over- 

 come tlie steam or vapour pressure due to the temperature of the 

 water in the condenser. 



Weight in-doors 29 t(jn - - = 04,9(30 lbs 



.Stulling box friction, say - - z= 501 



412 i,„.i,es X 1 fathoms' X bv ■2-01.54 lbs = 3,439 



Gross load in lbs. 

 Quarter of eft'ect load ;= 

 gross power 



l-5th 



= 68,900 load for eft'ect. 



:= 17,224 engine's resistances. 



=: 80,124 lbs. 

 Gross steam pressure on the shaft. 

 In a recent communication by Mr. Wicksteed, relative to the suc- 

 cess of the Harvey's and West's patent double beat valve, the pump 

 stroke is stated to be nine feet, and consequently 90 feet of motion at 

 10 strokes per minute. Taking the gross pressure in the shaft at 

 80,124 lbs. X 90 feet, = 7,751, IGO lbs. one foot high, we have 

 7,751,100 



—rjr- =: 23.J gross horse pow er. 



33,000 ^ ^ 



In consequence however of the prevalence of the method among 

 practical engineers of deducting the resistances due to vacuum, im- 

 ])erfections from the observed average indicator pressure, and calling 

 the result average steam pressure (a quantity I should feel disposed 

 to term a worthless mean between gross and nett power of no practi- 

 cal value, and absokitely injurious in tending to mislead in estimates 

 of pounds of water used in the cylinder), it would not be fair to con- 

 trast that which is proposed to represent the gross povver of a good 

 Cornish engine, until it has been ascertained whether the observed or 

 calculated gross steam power in the Lancashire factory engine has 

 been given. 



The error will be in its favour if an allowance is added of -^rj, 

 perhaps, for this practise, while the engine's resistance, ought perhaps 

 to be taken higher than one-fifth of the gross power to allow for the 

 greater friction of smaller cylinders working at a high power, if re- 

 quired ; it appears to me that the one-third allowance should be de- 

 ducted from the nett power thus obtained, for a duty estimate, giving 

 20 millions as a rough approximation. 



34,754,432 

 One-twelfth .... — 2,890,202 



One-fifth engine resistance 

 One-third shaft-work - 



37,050,031 

 ; 7,530,120 



30, 120,508 

 : 10,040,109 



Duty = 20,080,339 



My object is to recommend tlie simple classification here used, sub- 

 ject to any corrections of engine or pitwork resistances, conceiving 

 if attention be called to this subject, it will soon lead to the adoption 

 of correct methods, which will facilitate the connection of theoretical 

 and practical views of steam engines. 



I am, Sir, 

 Your obedient servant, 



John S. Enys. 

 January, 1810. 



Discovery of a Cnt'cru. — As the workmen were employed in blasting the 

 rocks near the foundation of one of the Clifton suspension bridge piers, a day 

 or two since, they discovered a small uj)cning. On i(s being examined, it was 

 found to lead to a small cavern extending tilty-scven feet below the surface 

 of the gro\md, nearly in a perpendicular direction. The exploration was 

 made by Dr. Fairbrothcr, with the assistance of one of the workmen. 

 There were several chambers at intervals, but the descent is diflicult, and 

 can only be made with the assistance of ropes. The air is tolerably pure, so 

 that the candle burnt freely during the whole of the tiinc (nearly two hours). 

 At the bottom, the air was found to be excessively hot, so that the perspira- 

 tion flowed freely. In other respects the cavity presented nothing remark- 

 able, beyond the ordinary appearance of fissures formed by the raising of 

 the strata of lime-stones by some extraordinary convulsions of nature. 



THE CORNISH ENGINE, 



AT TtiE E.\ST LONDON WATER WORKS. 



As tlie above engine is likely to become an object of considerable 

 interest to engineers, we determined upon paying a visit to the Water 

 Works at Old Ford, for the purpose of obtaining correct information 

 as to her dimension and mode of working. (Jn our arrival ;it the 

 works, Mr. Wicksteed, the engineer to the Company, immediately 

 granted us permission to inspect the engine, and kindly ofiercd to 

 afford any infcn-matiun we might require, and for this jnirpose, accom- 

 panied us on our view, and readily answered every enquiry, explain- 

 ing at the same time, the general working of the engine. Before 

 ])roceeding to the detaiLs, we must offer our congratulations to the 

 directors of the Company, on the successful performance of the 

 engine, and we feel happy to find that the very large pecuniary 

 saving in fuel annually, by the adoption of the CornisTi engine, will 

 amply repay them for the spirited manner in which they came for- 

 ward to support their engineer against the almost unanimous opinions 

 of the London engineers, who generally pronounced the boasted per- 

 formances of the eugines in Cornwall to be preposterous. Through 

 the kindness of Mr. Wicksteed, we are now enabled to lay before 

 our readers practical data of the economic working of the engine at 

 the East London Water, Works, which we believe, is the first and 

 only Cornish engine that has been yet erected in the metropolis. 



The engine was originally intended for a Cornish mine, known by 

 the name of the "East Cornwall," it was designed by Mr. West, a 

 member of the Institution of Civil Engineers; it is upon the same 

 principle as the one designeil by the same gentleman, erected at the 

 Fowey Consols Mines, which has for several years past clone more 

 duty than any engine in or out of the county of Cornwall, and manu- 

 factured by Messrs. Harvey and Co. of Hayle ; it was purchased liy 

 the East London Water Works Company in 1837, and removed to 

 London and fixed in its present situation by Messrs. Harvey and 

 West, who have, by the superiority of the working of this engine, 

 and the faithful execution of their contract, given most unr|ualified 

 satisfaction both to the directors and to Mr. Wicksteed. 



Dimensions of ilie Engine. — The diameter of the steam cylinder is 

 80i inches, and length of stroke, 10 feet 3 inches ; the steam is 

 generated in the boilers, under a pressure of 351b. on the square inch 

 above that of the atmosphere, antl cut oft" when the piston has per- 

 formed about one-third of its stroke, it then expands during the re- 

 maining two-thirds, and in the suceeeding stroke is condensed to 

 form a vacuum on tlie opposite of the piston, to wdiich it passes 

 through the equilibrium valve in the return stroke, the engine being 

 single acting. 



By the use of the apparatus called a cataract, the engine can be 

 made to work from one (or less) to ten strokes per minute, as may be 

 required. According to the calculations of Mr. Armstrong in our 

 last Journal, the power of the engine is equivalent to 200l horses, 

 and by the statement of Mr. Enys in the present number, 235 gro^s 

 horse power. Mr. Wicksteed, however, informs us that the actual 

 weight lifted is 66,443 lbs. an average height of 9 feet each stroke, 

 which is equal to 18" 12 horses' power when the engine works one 

 stroke per minute, or 181*2 horses' power at 10 strokes per minute, a 

 velocity which Mr. Wicksteed deems the greatest this engine should 

 be worked at. 



Dimensions of the Pump. — The diameter is 41 inches, length of 

 stroke 9 feet 4 inches, quantity of water lifted at every stroke S2*5 

 cubic feet, or about 14i imperial barrels, which is a week's average 

 supply for a house. The plunger-pole of the pump, is loaded 

 with about 29 tons over and above the other end of the beam, and 

 this is the weight the engine has actiwlly to lift at every stroke. 



We were very much pleased with the quiet action of Messrs. 

 Harvey and We.st's patent valve, there we felt any perceptible vi- 

 bration, although we stood close to the pump ; we have given the 

 drawings and specification of the valve in another part of the Jour- 

 nal. 



The steam is generated in four cylindrical boilers, 27 feet 8 inches 

 long and feet 5 inches diameter, constructed on Mr. West's 

 Cornish plan ; the tops of the 4 boilers are covered over with fine 

 ashes, to prevent the loss of heat by radiation. The area of the 

 boilers exposed to the action of the flame and heated air, is very 

 great ; and the furnaces are constructed with a large surface of fire 

 grate, in jn'oportion to the coals consumed, for the purpose of adopt- 

 ing the principle of slow combustion, wdiich is here carried out to its 

 fullest extent, so much so, that when the furnace doors are opened, the 

 smoke at times comes out of the furnace doors into the stoke-hole. 



We must also state that the steam cylinder is surrounded wdth a 



K 



