14 VARIOUS INVENTIONS. 



erected my engine to evade the patent premium, but have 

 severely paid for their saving knowledge by accidents and 

 defects in their engineering ability. I have erected above 100 

 steam-engines on this principle, but never met with one accident 

 or complaint against them. To prevent mischief from bad 

 castings, or from the fire injuring the surface of cast iron, I 

 make the boilers of wrought iron, and always prove them with a 

 pressure of water, forced in equal to four times the strength of 

 steam intended to be worked with. 



" Some persons have worked those engines under a pressure 

 above 100 Ibs. on the square inch, but in general practice I do 

 not exceed 20 Ibs., finding under this pressure the piston will 

 stand six or eight weeks, and the joints remain perfect, and no 

 risk of bursting the boiler, it being made of wrought iron, and 

 proved by pressure before sent off; but cast-iron boilers may, 

 by defects not discernible, and are very apt to break by the 

 water being left low in the boiler, and if heated red hot, explod- 

 ing without the smallest notice ; but wrought-iron boilers, when 

 defective, give way only partially, without injury to anyone. 

 With respect to the erecting and management of the engine, 

 you need not have an engineer, for any common tradesman can 

 do this from the drawings and directions sent with the engine; 

 for, as I before informed you, farmers and their labourers set up 

 and keep in order the thrashing-machine engines without my 

 going on the spot or sending any person to assist them. I 

 never saw a steam-engine rolling malt, therefore cannot judge 

 the quantity the engine would roll, only by a comparison with 

 horse labour, against the consumption of coal, which will be in 

 some cases as about 42 Ibs. to one horse ; but where great speed 

 is required in the machine, the coal will be less, as steam- 

 engines make more revolutions in a minute than horse mills, 

 therefore the work is done with less friction. 



" I have several times applied the steam, after it has worked 

 the engine, to boil water and other purposes, with as good effect 

 as if the engine had not been there, therefore the work of the 

 engine will be a clear profit. 



" You say about a 1-horse engine. The boiler would be so 

 small that it would not be worth applying that steam to any 



