1{>6 Scientific Intelligence. — Arts. 



The proportion of the heating to the evaporating surface nearly 74 to 1 



Ft. In. 



<;. (30 wide ) 



steam J 4 jq average depth J- containing about 65 cubic feet. 



Chamber | ^ g j^^g j 



Diameter of the safety valve very nearly 5 inches, being 19 square inch 

 . area, which was loaded for a pressure on the square inch of 4 lb. 



Giving 70 for the load. 

 Of this, CC lb. of iron were placed in the boiler, and 10 lb. allowed as the 

 weight of the valve, rod, hook, handle, &c. The water used was the salt 

 water from Wallasey Pool, and filled into a large iron tank, the area of the 

 surface of which measured 32^ superficial feet. The boiler was placed under 

 an open shed ; the day was very c(>ld, with thick rain. No engine being at- 

 tached to the boiler, the exhausting apjiaratus was worked by a wheel and 

 band from Mr Laird's turning engine. The velocity of the circle of percus- 

 sion of the leaves of the exhausting wheel was determined to be about 77 feet 

 per second, or upwards of 52 miles an hour. IVtr Laird's engine is stated to 

 be a four-horse power. No determinate measurement was made, but the en- 

 gineers present computed that the power applied to turn the exhausting 

 ivheel was equal to that of two horses. The fire being lighted, the steam 

 was got up to 4 lb. pressure in 45 minutes, with a consumption of 2A cwt. of 

 coke. The expenditure at first was 8 lb. per minute, and gradually decreased 

 to 5 lb., averaging about CJ lb per minute for getting up the steam. The 

 steam began to rise in 27 minutes, after which the consumption of coke was 

 little more than 5 lb. per minute ; and at this period there would have been 

 a sufficient supply of steam to work the cylinders of an engine. The coke 

 employed was gas-coke of very bad quality, of which 34 cubic feet weighed 

 105 lb., giving 30 lb. for the weight of a cubic foot, or 3000 lb. as the weight 

 of 100 cubic feet. The same weight of St Helen's coal (that principally used 

 in steam-boats) measures G3 cubic feet. The cost of the coke used was 8s. 6d. 

 j)er ton, delivered in Liverpool ; the cost of smithy coke being 25s. per ton, 

 of which 3 J cubic feet weighs 115 lb., giving very nearly 33 lb. for the weight 

 of a cubic foot. When the steam was up, the water in the thick glass gauge 

 attached to the boiler standing at 74 inches, the two men stationed for the 

 ])urpose began to pump, a fresh supply of weighed fuel was placed on the 

 floor, and the following observations were made: — At 3h. 32m. began to 

 jiump ; at3h. Sim. IC cubic feet of water were evaporated ; at 4h. 12m. 27 cu- 

 l)ic feet of water were evaporated ; at 4h. 19m. 38 cubic feet of water were 

 evaporated, and 2 cwt. of coke consumed ; at 4h. 32m. 41 \ cubic feet of wa- 

 ter were evaporated, with a consumption of 252 lb. coke. From which it ap- 

 pears, that only 6 lb. of coke per cubic foot of water per hour was consumed ; 

 and the evaporation of a cubic foot of water per hour being generally con- 

 iiidered the measure of a horse power, the conclusion is, that the boiler was 

 a forty-horse boiler, and that the quantity of fuel i-equisite to work it is 2J 

 cwt. per hour, tlie expense of which is 12|d. ; and as the consumption dimi- 

 nishes after the first hour, the expense of fuel will probably not exceed Is. 

 ■jier hour for the forty-horse boiler. (Signed) Alexaxdeh Nijimo, C. E. 

 CiiARi-ES L. ViGNOLES, C. 'E.— Waterloo Hotel, Liverpool, 20th Bluy 1830. 



