18G 
Application of Steam Power 
only impeding- the onward progress, but tending to damage very 
adhesive clay by their pressure ; while the stirring up of land 
already tilled and lying fallow seems scarcely practicable, owing- 
to the great amount of power that would be needed for mere 
locomotion. The other objection is, that the number of wheels, 
running-bearings, and working parts, makes the machine difficult 
and expensive to keep in order, as well as very costly in the first 
outlay. The economy, however, no less than the superiority of 
the tillage, has proved a great success ; the amount of work done 
having been from 4 to 7 acres a day, according to the description 
of soil and depth of work, at a total estimated expense of 55. or 
Qs. up to 95. or IO5. per acre, including 2 men, coal, water, &c., 
and 15 per cent, wear and tear, and interest for 200 days in the 
year, tirst cost being 800/. 
An engine has been manufactured by Mr. W. H. Nash, of 
Cubitt Town, Isle of Dogs, London, in which the machinery is 
in certain respects simplified and improved. The digging- 
cylinder resembles the one already described, being made of 
quarter-inch plate-iron, though it is 8 feet wide, and of 2 feet 
9 inches diameter, the tips of the cutters being 10 inches out 
from the cylinder, and so describing a circle of about 4| feet 
diameter; but instead of having gudgeons working in plummer- 
blocks at the ends, it rotates upon trunnicms or annular bearings 
of about 8 inclics diameter. A shaft, driven by cranks and con- 
necting-rods from the engine crank-shaft, passes througli the 
centre of the cylinder, rotating however in the opposite direction ; 
and at each end of this shaft, just within tlie cylinder, is an 
8-inch pinion, which, by means of two intermediate pinions of 
rather larger size (supported by the framing through the trunnion 
or hollow bearing), drive an annular wheel (composed of lour 
toothed segments) affixed to the inside of tlie cylinder. The 
movement is somethina: like that of Barrett and Exall's Safety 
Horse-work, and is tlie same at both ends of the digger ; the 
wlieel-work being all boxed up within the cylinder, but accessible 
by the removal of ])ortions of the plate-iron for the purpose. 
The engine crank-sliaft is underneath the boiler, and passes 
tin-ough the hollow bearings of the main travelling-wheels 
on both sides the machine, this point being also the ful- 
crum upon which the lever-frame, supporting the digger, is 
allowed to rise and fall. But the next machine is proposed to 
be constructed with outside bevel-wheels, and shafting instead 
of the internal wheels and connecting-rods. 
There is an arrangement of gear-work for driving either of the 
main carriage-wheels, or both, or disengaging either of them at 
pleasure ; and, while there is a slow motion for use when culti- 
vating, tliere is a faster speed of about two miles per hour for 
