186 
Steam Engine. 
4thly. If my improvements be applied to one of the 
engines known by the name of Watt’s double engine, the 
working cylinder must have no direct communication 
with the boiler, but must be made to communicate at its 
top and bottom alternately with the lower and upper part 
of the smaller added cylinder, or simply, as the case may 
be, at its top and bottom, with the steam measure, which 
has a direct communication with the boiler; the effect of 
which must be sufficiently obvious from the details I 
have already given respecting the nature of my invention, 
and the way in which the same is to be carried into actual 
practice. 
5thly. With regard to steam engines, in which the se- 
parate steam measure may not be thought advisable, the 
same may be improved by the application of my aforesaid 
discovery, by making the boiler, and the steam case or 
cases in wliich the working cylinder or cylinders is or are 
inclosed^ much stronger than usual ; and by altering the 
structure and dimensions of the cocks, valves, slides, or 
other means of admitting steam from the boiler into the 
cylinder or cylinders, in such a manner as that the steam’ 
may be admitted very gradually by a progressive enlarge-^ 
ment of the aperture, so as at first to wiredraw, and after- 
wards admit more freely the same. The reason for this 
precaution is this : Steam of such great elastic force as I 
employ, if admitted suddenly into the cylinder or cylin- 
ders, when more than one working cylinder is employed,, 
would strike with a force that would endanger the safety 
and durability of the engine^ The aperture allowed t® 
the valve, cock, or other contrivance for admitting steam 
into the cy linder or cylinders, should be regulated by the 
following consideration If the intention is that the en- 
gine should work only, or almost wholly, by condensatio% 
the steam in passing into the cylinder or cylinders should 
be forced to wiredraw itself, as I have already said, but so 
