6GG On Compound Engines for Agricultural Purposes. 
There are many other questions affecting these considerations. 
Among them are the loss of draught when the exhaust escapes 
into the chimney at a pressure only a little above the atmosphere, 
which may neutralise the first gain in weight of the boiler by 
rendering more heating surface and larger tubes necessary ; but 
the above statements show the most salient features of the gain 
to be anticipated from the use of compound engines. 
Probably for large traction engines, two cylinders side by side 
will be the best arrangement, as an engine will thus become 
more handy, having no dead centres, and a simple bye-pass 
arrangement would admit live steam from the boiler to the low- 
pressure cylinder, to give the maximum power for facing heavy 
gradients and starting. 
It is noteworthy in this place to remind our readers that we 
in our own practice have used the compound principle in our 
beam engines for mill purposes and pumping for forty years 
past ; and that during the last fifteen years compound engines 
have become almost universal for marine purposes. They are 
now on the eve of being introduced into railway locomotives, 
and we believe will be very largely used in them in the future, 
perhaps almost universally. 
It is also interesting to note that Mr. Thornycroft, the famous 
builder of high-speed steam-launches, found years ago that he 
could reduce the gross weight of his engines, boiler, water, and 
fuel, to produce a given power for a given time, by using com- 
pound in preference to simple engines. If he gained an advan- 
tage from such a change, it is reasonable to suppose that traction 
and ploughing engines may similarly be benefited by it, though 
it is fair to say that the gain is more important in condensing 
than in high-pressure engines. 
High-pressure steam has a greater effect in promoting economy 
in a compound than in a simple engine, especially when the 
exhaust takes place above the atmospheric pressure. It is 
therefore likely that all makers of compound agricultural engines 
will eventually adopt a steam-pressure of something like 120 
to 150 lbs. We think it well tlaat non-professional men should 
know that a boiler properly designed for 150 lbs. steam, is as 
safe as one designed with similar m,argins of safety for 60 lbs. 
steam ; and we hope the prejudices of the public against high- 
pressure steam will shortly disappear altogether. 
Nearly all railway locomotives and traction engines work at 
about 150 lbs. pressure, and accidents due to the failure of their 
boilers from weakness are of extremely rare occurrence. 
It may be said, will a compound portable engine, working 
with 80 lbs. steam, when tried on the brake, beat the economic 
performances of the Claj ton and Shuttleworth and Reading 
