Steam Engine, 183 
the steam by which the engine is worked ; and their re- 
spective piston rods are so connected with one another, or 
with other parts of the machinery, that the pistons may 
act together* 
3dly* With regard to steam engines which are already 
constructed, I improve the same by adding thereto a 
small cylinder or measure for the steam admitted to the 
working cylinder ; this improvement may be introduced 
with great advantage into the steam engines constructed 
according to Mr. Watt’s improvements ; which small 
cylinder may be either employed only as a measure of the 
steam, or a piston may be worked in it by the expansive 
force of the steam, before it be allowed to pass into the 
present working cylinder or steam vessel, which in that 
case must have no direct communication with the boiler, 
but must be supplied with steam through the medium of 
the small added cylinder or steam measure. To make 
this more intelligible, suppose the steam measure or small 
cylinder added to one of Mr. Watt’s single engines, or to 
one of similar construction, and that the small added cy- 
linder is furnished with a piston to work by the expansive 
force of the steam, while the larger cylinder works by con 
densation ; then all that is necessary is, that the top of the 
smaller added cylinder be connected with the boiler, and 
furnished with a cock or valve to shut off the steam, and 
that the boiler be of sufficient strength : let a pipe pass 
from the top to the bottom of the smaller added cylinder, 
furnished with a cock or vah e, by which a communica - 
Uon may be made between the two sides of the piston in 
the said cylinder ; let a pipe also pass from the bottom oi 
the smaller cylinder to the top of the larger ; let the larger 
cylinder, as is now commonly the case in practice, have a 
pipe passing from its top to its bottom, by which a com > 
munication can be made betw^een the two sides of the 
piston in the large cr^linder ; and let the large cylindei 
