190 
Application of Steam Power 
The tines are used for roughly breaking up without invert- 
ing : to produce partial inversion they are placed in pairs or 
triads together. To give more general inversion, the spade- 
form shares are used, moving the subsoil and inverting the sod, 
and leaving the roots exposed ; Avhile for wet clay land, angular 
cutters or shares are used ; and for light soil, the broad shares, 
inverting the whole. The digging shaft is quickly lifted or 
depressed by screws, bevelled wheels, and a crank for the pur- 
pose. The speeds of revolution and progression are so timed 
that the engine advances 9 inches for each revolution of the 
digger ; and there being two cutters in one circle at opposite 
diameters, eacli cutter takes a forward bite of Ah inches. But 
this may be varied by changing a spur-wheel and pinion in the 
propelling gear for others.* In the trials the speed of the digger 
ranged from 60 to more than 80 revolutions per minute ; the 
rate of travelling, therefore, varying from about half a mile to 
about two-thirds of a mile per hour. 
The engine is of 8-horse nominal power, having two 5j-incli 
cylinders of 10-inch stroke ; but being worked up to 90 lbs., 
and even 95 lbs. pressure, and making 140 to 150, and some- 
times up to 180 revolutions per minute, was evidently giving off 
more than double that power. The digger-shaft being 7 feet 
in length, this breadth of ground was sliced up and broken to 
pieces to a depth of 5 or G inches, the knives dipping rather 
unequally (owing to the ground being in awkward ridges and 
furrows), and sometimes the digging was lowered to 7 or 8 
inches. The narrow tines, with spaces between, tore up the 
soil into small fragments ; the 5-inch broad spades (of which 
there were 24 — two on opposite arms of the 12 bosses) cut the 
ground into curved wedge-shaped spits, and, turning them over 
the shaft, delivered them loosely broken, and mostly in an 
inverted position, with the soil well exposed. 
The frequent stoppages, owing to the new and untested mecha- 
nical details, rendered continuous work impossible ; but, from ob- 
servations of a few minutes' operation at a time, the rate of advance 
appeared to be as already stated, — equivalent to 4i to nearly 6 
acres in 10 hours, or less when the time for turning at the ends 
is deducted. The expense, including 15 per cent, wear and tear, 
and interest on 440/. for 200 days in a year, would probably be 
from 7s. to 9s. per acre. The length of the machine is about 13 
feet, and the weight when in work about G tons, which on that 
liglit, diy, lea ground, sunk the wheels very considerably into the 
ground, and would be very objectionable on wet clay. 
* See an enp^raving of this machine in the Report on Implements at Chester. — 
Journal, vol. xi.x., p. .'321, 322. 
