310 



Intelligence and Miscellaneous Articles. 



Mr. Watt's engines, well constructed and well managed, will raise 

 twenty-five millions for an average. They are still the only engines 

 used in London for water-works, and in many districts for draining 

 mines ; they were the only engines used in Cornwall in 1814, when 

 Mr. Woolf set up his first engines there. Under favourable circum- 

 stances, such as having little work to do, keeping up the steam as 

 strong as can be retained in the boiler without overflowing the feeding 

 pipes of eight feet high, and working with the utmost extent of ex- 

 pansive action that those circumstances will allow, using good coals, 

 clean water, plenty of cold condensing water, and the boiler, cylinder 

 and steam-pipes being properly clothed, — a well constructed engine 

 of Mr. Watt's may raise thirty-two millions ; but that is the utmost, 

 and cannot be maintained in regular working. On the other hand 

 a number of engines working incessantly at deep mines, under ordi- 

 nary management and average circumstances, will not reach twenty 

 millions, as is shown by the following account of the average per- 

 formance of the engines in Cornwall in 1813 and 1814, when they 

 were all worked on Mr. Watt's system of low-pressure steam acting 

 expansively in one cylinder. 



Date 



of 

 Year. 



Aggr. of the Engines in Cornw. 



Aver, per Engine. 



Annual Per- 

 formance of the 

 best Engines. 

 Millions. 



No. of 

 Engines 



Aver. 

 Mills. 



Bushels 

 per Ann. 



Horse 

 Power 



Bushels 

 per Month 



Horse 

 Power 



1813 



1814 



24 

 29 



19-38 

 20-37 



770076 



1002563 



861 



1176 



2672 

 2880 



35-9 

 40-5 



26-65 

 31-99 



1828 

 1829 



56 

 53 



37*33 



41-22 



1165866 2508 

 9854352342 



1735 

 1550 



44-8 

 44-2 



77-29 

 76-23 



In 1813 the highest performance attained by the best engines on 

 Mr. Watt's system did not reach thirty millions, and the performance 

 of all the engines averaged less than twenty millions ; but in 1829, 

 when all the engines were worked on Mr. Woolf's system of high- 

 pressure steam acting expansively in one cylinder, the best of those 

 engines averaged seventy-six millions, and the whole number (being 

 more than twice as many as in 1813) averaged forty-one millions. 



The great cause of the superiority may be thus explained : Mr. 

 Woolfs engines are worked by high-pressure steam, which is retained 

 in the boiler to an elasticity of between twenty-five and forty-five 

 pounds per square inch more than the atmospheric air. Steam of 

 that elasticity may be expanded to fill between five and eight times 

 the space it occupied when first admitted from the boiler into the 

 cylinder ; and yet it will have a sufficient force to impel the piston 

 with as much effect, during all that great extent of expansive action, 

 as can be done in Mr. Watt's engines when the expansion is only 

 from one space into two : hence Mr. Woolf's system renders the ex- 

 pansive action available to a greater extent than can be done in Mr. 



Watt's 



