594 The Trials of Light Portable Motors at Plymouth. 
irregularity of the compression line of the diagram appears to 
be due to the expansion of the steam into the passage way of 
the Trick valve. The regulation of the admission in this engine, 
by a governor acting on the slide valve, was a much better 
arrangement than that shown on any other engine. It would 
have the effect with a lighter load of cutting off the steam sooner. 
In the opinion of the Judges, therefore, this engine would have 
shown a gain of economy with a rather less load. The very 
large cylinder condensation shown is hardly explainable, if the 
engine was not supplied with wet steam. With a rather lighter 
load, the boiler would have been less forced, and probably in 
that case there would have been a distinct reduction of the 
cylinder condensation. 
The diagrams for the compound engine of Messrs. Simpson, 
Strickland & Co. (fig. 5) are decidedly better than those for the 
simple engines. The dryness fraction during the expansion in 
the high pressure cylinder varied from 0*70 to 0 - 64, so that there 
was less waste of steam than in either of the single cylinder 
engines. Nor is this all. During the low pressure expansion 
the dryness fraction was 0'802 to 0831, showing that a con- 
siderable fraction (about one-tenth) of the water in the high 
pressure cylinder was evaporated in the engine, and acted as 
steam doing work in the low pressure cylinder. The real ratio 
of expansion in this engine was 4 - 4, and it is to this greater 
expansion, together with the less waste of steam by condensation, 
that the very remarkable gain of economy in this engine com- 
pared with the others is due. There is obviously a good deal of 
waste expansion in this engine, the actual diagrams filling up 
very badly the space between the two saturation curves. That 
is a defect due in part to the very simple and rather crude 
mode of compounding adopted. It should be remembered, how- 
ever, that waste expansion, like wiredrawing, is not entirely a 
loss. Both these actions tend to dry the steam, and so to reduce 
the prejudicial action of the cylinder sides. 
Looking at the diagrams of the single cylinder engines, one 
is driven to ask whether an engine in which half the steam is 
condensed before it has done any work, and the whole of the 
heat expended in producing it thrown away during exbausfc, 
can represent good engineering practice. When one finds that 
these engines were using 57| and 04| lb. of steam to the 
indicated horse-power per hour, and that they required 8'4G and 
9 06 lb. of the best Welsh coal to the indicated horse-power 
per hour, one is no doubt tempted to think that they represent 
very bad engineering practice, and that the makers must have 
been culpably negligent or grossly ignorant in designing the 
