SECT. ,.] THE STEAM ENGINE. 37 



hours in its best state, and seven in its worst state. Under these circumstances 

 it made ten strokes per minute, and raised seventy cubic feet of water twenty feet 

 high in a minute. 



According to this statement, in the best state of the engine, 87 Ibs. of coal were 

 consumed in 2 hours or 120 minutes, and 1400 cubic feet of water raised one foot 

 high per minute; or 1400x120=168,000 cubic feet by 87 Ibs. of coal, which 

 multiplied by 62|- Ibs., the weight of a cubic foot of water, and divided by 87, 

 gives 120,000 Ibs. for the load raised one foot by one pound of coal ; which is 

 about one half the effect produced by an engine with a piston and Watt's con- 

 denser, and less than the effect of the common atmospheric engine as used for the 

 coal mines. 



An attempt was also made by John Nancarrow, to improve Savery's engine, by 

 condensing in a separate vessel ; but the nature of the engine does not permit of 

 this being applied with much effect. 



1799. MATTHEW MURRAY ; died 1826. 



46. In the construction and improvement of some of the parts of engines, 

 much was done by Mr. Murray, of the firm of Fenton, Murray, and Wood, of 

 Leeds. These improvements were made the subjects of patents ; and though it 

 appeared that some of them had been before used by Boulton and Watt, they did 

 not become publicly recorded till Mr. Murray obtained patents for them. 



In his patent of 1799, in order to save fuel, Murray proposed to place a small 

 cylinder with a piston on the top of the boiler, connected to a rack, by means of 

 which the force of the steam within the boiler opens or closes the damper fixed 

 on an axis in the chimney, thus increasing or decreasing the draught of the fires, 

 so as to keep up a regular degree of elastic force in the steam. Mr. Murray also 

 thought some advantage would be gained by placing the steam cylinder in a 

 horizontal instead of a vertical position, with a view of rendering the engine more 

 compact than the usual construction ; he also adopted a new method of converting 

 the reciprocating motion of the piston rod to a rotary one of equal power, by means 

 of a property of the rolling circle, and showed how to fix the wheels for producing 

 motion alternately in perpendicular and horizontal directions. J 



47. Mr. Murray's patent of 1801 was for six different objects: First, for a 

 method of constructing the air pump. Second, for a method of packing stuffing 

 boxes, &c. by bringing the moveable parts of each in immediate contact, which 

 prevents the piston rod receiving any oblique pressure, by the lid being screwed 

 down more upon one side than the other. The third and fourth methods relate to 



1 Repertory of Arts, vol. xi. p. 311. Old Series. 



