596 The Trials of Light Portable Motors at Plymouth. 
steam pressure, a low speed of piston, and for simplicity a single 
cylinder, as governing conditions. Given those governing con- 
ditions, there is no reason for supposing that the engines tried 
were bad engines, 1 or that any others in the market which could 
have been put into the competition would have achieved sensibly 
better results. For the conditions assumed are exactly those 
which involve as a practically unavoidable consequence an 
enormous cylinder condensation, and a condensation which 
increases sc fast with any increase of expansion that full steam 
must be carried through a great part of the stroke. Some 
amelioration might be obtained, if a moderate super-heating can 
be given in the boiler, but this is almost the only way in which 
any sensible improvement is to be gained. 
But are the conditions of moderate pressure, low speed, and the 
extreme of simplicity rightly selected ? It appears that makers 
have overlooked the fact that these conditions not only involve 
inefficiency in the engine and consequent cost in coal, and 
increased cartage of feed water, but they also involve as a 
consequence that the engine and boiler are large, heavy, and 
costly. The results for the engine of Messrs. Simpson, Strick- 
land & Co. show that we may have, with very little additional 
complication, three times as much power per cwt. of weight 
of engine and boiler, and at the same time use less than half 
the coal, and little more than half the feed water. 
Hence the moral of the trials is that small single cylinder 
steam engines, such as those tried, are only defensible on the 
assumption that a quicker piston speed, a somewhat higher 
steam pressure, and a second cylinder, are altogether unsuited 
to engines for agricultural purposes. If economy of coal were 
alone in question, perhaps this view might be plausibly defended, 
but it can hardly be adhered to when the greater portability 
of the other type of engine is also taken into account. v 
It may be admitted that the engine and boiler of Messrs. 
Simpson, Strickland & Co. was not an entirely satisfactory speci- 
men of its class. But the results show that it belongs to an 
altogether better class than the engines competing with it. And 
it shows exactly the direction in which improvement can be 
made, if makers can be persuaded to abandon a type of engine 
which has been adopted largely in ignorance of its inherent and 
incurable defects. 
Petroleum Engines. 
Two petroleum engines were entered for competition, in both 
of which the petroleum or shale oil was vaporised, mixed wit h 
1 The reasoning here applies to the engines only, not the boilers. Messrs, 
Adams's boiler was not a good one. 
