378 
Five Years Progress of Steam Cultivation. 
clutclies) close at hand, under the command of the engine-man. 
Mr. Fowler's " double " engines supply themselves with water by 
simply running disconnected with their drum or propelling wheels. 
In Messrs. Savory's arrangement the cylinders are necessarily of 
short stroke, giving out their full power only at a high number 
of revolutions per minute (unless at an excessive pressure of 
steam) ; and, by driving the drum directly without reducing gear, 
too great a speed is obtained for any implement to work steadily. 
Travelling at a pace of more than 4 miles per hour (5 miles 
per hour in light work), the implement not only makes im- 
perfect work, but incurs great risk of damage from land-fast 
impediments ; and, besides, a broader cultivator, at a pace of 
2J to 3 miles per hour, would waste less time, owing to the 
few number of bouts, each with its steady commencement and 
slackening of speed toward the close of the journey. The faci- 
lities of the tw"in-engine principle are well illustrated by this set 
of apparatus, which, without the assistance of any horse, 
brought itself along 30 miles of up-and-down-hill road from 
Gloucester in one day, and shifted from field to field, losing but 
a few minutes in gathering up or leading-out rope and taking up 
position ready for work. 
One more invention remains for notice. ^Ir. CoUinson Hall, 
of Xavestock, Romford, Essex, substitutes for wire-rope a chain, 
formed of |^-inch round steel rods, 18 inches long, coupled to- 
gether by pairs of flat plates 4 inches long, with connecting 
rivets ; and an endless chain, thus made, passes one half-turn 
round a drum beneath a moveable-engine boiler, and similarly 
round a pulley upon a self-travelling anchorage at the further end 
of the field. But the drum and pulley are polygonal instead of 
circular ; and the link-chain is hauled by means of cog-teeth upon 
the drum taking into the apertures provided by the coupling- 
plates of the chain. The breaking strain of the plates (the weak- 
est point) has been found to be about 14 up to 22 tons ; the cjiain 
being probably stronger than wire-rope of equal weight. The 
merit of the invention is in its supposed durability. The rods 
and plates of this link-chain (exhibited by Messrs. Turner 6f Ips- 
wich) present but little appearance of attrition after having 
ploughed 400 acres ; and it is affirmed that not one rivet has yet 
been broken. The wear must take place chiefly on the ends of 
the rivets and in the eyes in which they work ; but if the rivets 
be purposely made of softer metal, they alone will wear away, 
and the whole of the 2800 rivets in 800 yards' length of chain 
may be replaced for some 30.s\ As the chain (from Its sidelong 
rigidity) will not wrap upon a drum, it is unadapted to the sta- 
tionary-windlass system, where greater economy of rope is most 
of all desirable ; and, moreover, this necessitates a tedious unbolt- 
