22 THE HISTORY OF [SECT. i. 



and turn them to account in managing the action of steam ; his talent was chiefly 

 confined to improving the construction and proportions of existing machines, by 

 selecting the best methods known, and making experiments : accordingly, we find 

 he designed a portable atmospheric engine to make trials upon, in 1765 ; and these 

 experiments he was preparing for in 1769. 1 Smeaton afterwards directed the 

 erection of several large atmospheric engines, and brought them to a degree of 

 perfection which has not been exceeded in later times. I propose briefly to follow 

 through the most interesting of his inquiries ; commencing with his portable 

 engine. This seems to have been the first attempt to make an engine capable of 

 being removed from place to place. The fire place was formed entirely within the 

 boiler ; and in the place of an ordinary beam, a wheel 6'2 feet in diameter, with a 

 chain, communicated the motion from the piston to the pump rod. 



The diameter of the cylinder was eighteen inches, its area, in circular inches, 324 

 inches ; and allowing seven pounds to the inch, which such a cylinder, he remarks, 

 would very well carry, we have 2268 Ibs. The number of strokes per minute 

 is stated to be ten of six feet each ; hence the effect is 2268 x 10x6=136080 Ibs. 

 raised one foot, or four horses' power : he reckoned it equivalent to six horses ; and 

 therefore his value of the horse power is 22680 Ibs. raised one foot high per 

 minute, instead of the usual standard of 33000 Ibs. 



Respecting fuel, he remarks, it has been found by experience that a two feet 

 cylinder requires 174 Ibs. of Newcastle coal per hour ; which, reduced in the ratio 

 of the capacity, gives ninety-seven pounds and a half per hour for the eighteen 

 inch cylinder, or a four horse engine, according to the common application of fire ; 

 but he had reason to think an engine constructed like his would not require above 

 sixty-five pounds per hour for a four horse engine. 



The fire place was of a spherical figure, of cast iron, and entirely within the 

 boiler ; the coals were introduced by a large pipe from the outside of the boiler to 

 the fire place, and the smoke passed off by a curved pipe with an iron funnel to 

 promote a sufficient draught. The ashes fell through a pipe covered by a grate 

 eighteen inches diameter, the whole being joined to the boiler by proper flanches, 

 and always covered with water. In so short a flue the force of the fire cannot be 

 wholly exhausted within the compass of the boiler, therefore the curved pipe was 

 surrounded by a copper vessel adapted to its shape, into which was brought the 

 feeding water, that it might be raised to a greater degree of heat than if brought 

 immediately from the hot well into the boiler. It is also obvious, that by this 

 arrangement the coolest part of the water comes in contact with the flue, to take 

 the heat from the smoke before it ascends the chimney. The bars of the grate 



Reports, vol. i. p. 223. and ii. 338. 



