Mr Impnnmnent an Sieam-^Engmes. S05 
18. Account of Mr Stein‘‘s Improvements in Steam-Engines. 
This ingenious contrivance, of which we can only give a 
brief, notice, is the invention of our countryman Mr Robert 
Stein, formerly of Edinburgh. A general view of it is given 
in Plate IX. Fig. 8., and the object of the invention may be 
stated to be for raising steam by means of heated air, and after- 
wards employing the steam so raised, and the heated air com- 
bined with a portion of steam to elevate the piston of a double 
steam-cylinder. By the hopper «, the fuel is introduced at 
suitable periods by the revolution of the fluted roller 5, which 
is fitted so closely as to prevent the admission of air, and the 
escape of the heated air within. The cinders and dust are dis- 
charged below through a similar air-tight apparatus. When 
the fire is lighted, a strong blast of air is thrown into the fur- 
nace through the pipe c, and this air, when heated and expand- 
ed, is conveyed along the pipe d to the high pressure cylinder 
where it works the piston, and escapes by the eduction-pipe J. 
The expansive force of this rarifled air is increased by a jet of 
water occasionally admitted among the coals in the hopper 
which, descending into the fire, is converted into steam. The 
heated air, in passing along the pipe d, and through the boiler f 
converts the water into steam, which, ascending through the 
pipe works the piston in the low-pressure cylinder A, and 
escapes by the condensation-pipe L The temperature of the 
furnace, and the quantity of elastic vapour generated, are regu- 
lated by means of’ a stop-cock in the blast-pipe c, which has 
two passages, one going above, and the other below the fire. 
If the expansive force of the air in d is too great, it will raise 
up the loaded piston m, and by means of the chain passing over 
the pulleys Zf, the handle of the stop-cock h will be elevated, 
and thus partly close the passage of the lower branch of the 
blast-pipe, which goes below the fire. When the heated air in 
d has top little elasticity, the piston m sinks by its own weight, 
lifts the lever of the cock opens the lower branch of the 
blast-pipe, and clpses the upper one. A fuller account of this 
invention, and of some of the other ingenious contrivances 
