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VII. — The Comparative Advantages of Fixed and Moveable Steam- 
Poiver, and of Single or Doiihle Dressing Tlir asking-Machines. 
By R. Vallentine. 
Prize Essay. 
The comparative advantages of fixed or moveable steam-power 
obviously depend very much upon a variety of special circum- 
stances. On large scattered farms, having several sets of out- 
buildings at which straw would be required, a portable engine 
will of course be most suitable, if not indispensably necessary ; 
and where steam-cultivation is also to be carried on, there would 
be a double advantage in the power being moveable. On some 
large farms, however, having central buildings, in which a great 
deal of thrashing is done besides grinding, chaff-cutting, &c., so 
as nearly to occupy an engine, a fixed power will prove most 
economical, even although steam-cultivation be carried on by a 
separate moveable power. But generally, where a portable engine 
can be made fully available for both thrashing and cultivation, 
the cost of both operations is very much reduced by dividing 
between them the first outlay and percentage of maintenance, 
instead of these being all charged to either the corn thrashed or 
the land cultivated. Instances are numerous where in practice 
one moveable engine is thus found sufficient for every purpose 
required. Again, there are many farms provided with two sets 
of buildings which require a good deal of thrashing at each. 
In such cases, if letting out for hire be not contemplated, I think 
a moveable engine with fixed thrashing-machines preferable to 
one moveable machine ; since besides other important advantages, 
to be described afterwards, two fixed thrashing parts cost no more 
than one portable machine, whilst the cost of maintenance is much 
less. 
Personal experience with every variety of steam thrashing- 
machine falls to the lot of few, if any ; although personal expe- 
rience of the use of some machines, and the observation of others, 
are possible enough. From all I have seen, and the chief of what 
I have heard, double-dressing machines, or rather those which 
are intended for dressing the corn so as to prepare it at once for 
market, do not succeed. There are times when the corn to be 
thrashed is of very uniform quality and condition, when a very 
fair and well-dressed sample may be obtained by blowing out a 
great deal of offal and light corn, with some that is good ; but, as 
a rule, the attempt to turn out the corn ready for market from the 
thrashing-machine is attended with loss. With the best engine- 
driver and the best feeder, there are times when the machinery 
goes slower than is desirable for driving all the light corn and 
short straws out of the bulk : it is then impossible to have the 
