The Evolution of Agriculiuml Imi)lements. 
253 
coal is dear and the climate dry enough to permit of grain being 
threshed very soon after it has been harvested. 
Head and Schemioth, in 1872, were among the first to experi- 
ment on the combustion of straw in steam-boilers, which they 
accomplished by fitting a feed-box and pair of rollers to the 
furnace-door of an ordinary portable engine. The feed-rollers 
are driven by a strap from the crank shaft, and force straw 
into the furnace in a thin, fan-shaped stream. The fuel is thus 
held in suspension, so to speak, for a short time, allowing the 
separated stalks to become immersed in the fiames, while pro- 
vision is made for the ingress of large quantities of atmospheric 
air to the fire-box. The consumption of straw in Head and 
Schemioth’s engine is approximately from 15 to 18 lb. per 
horse-power per hour. 
Messrs. Clayton and Shuttleworth have introduced a straw- 
burner which consists in the addition of a combustion chamber 
to the ordinary firebox, the two being separated by a bridge 
and baffle-plate, and it is claimed that the increased space and 
heating surface obtained by this arrangement suffice, together, 
for the complete combustion of the straw. Messrs. Clayton 
and Shuttleworth are responsible for the statement that this 
engine consumes only 14 lb. of straw per horse-power per hour. 
Elworthy’s patent straw-burner, manufactured by Clayton 
and Shuttleworth, is applicable to the ordinary portable engine, 
and consists of a tubular mouthpiece, taking the place of the 
firedoor, of a cast-iron hopper to fit the lower part of the inner 
firebox, provided with rocking grate-bars which can be agitated 
by a handle from without ; and a set of baffle-plates extending dia- 
gonally across the upper part of the firebox, which cause the flames 
to play upon the firebox sides before passing through the tubes. 
The calorific value of straw is as 1 to compared with 
coal, or, taking the relative local values of coal and straw into 
consideration, the use of the former would cost 3^ times more 
than the latter in countries like Kussia and Hungary. In 
England, on the other hand, coal is the cheaper fuel by 5 to 1, 
partly because of its own low price, and partly because of the 
high price of straw. 
Petroleum Engines . — To Messrs. Priestman Bros, belongs 
the credit of having demonstrated the suitability of the petro- 
leum engine for farm purposes. This motor proved moi’e 
economical of fuel than good portable engines at the Plymouth 
trials of 1890, while the character of the petroleum employed is 
such as to remove all fear of accidents from its use. It is probable 
that there will be an increased use of petroleum motors for 
agricultural purposes. 
VOL. III. T. s. — 10 
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