182 
Application of Steam Power 
furnished with radiating points or cutters. The rotary motion 
of the discs is communicated from the steam-engine, from which 
also the progressive motion of the machine is derived. The two 
motions are independent of each other, and so arranged that a 
rapid motion may be given to the cutters, Mhile the progressive 
motion is slow or suspended altogether, as at commencing. The 
gearing is such that the respective speeds can be varied at 
pleasure to suit the nature of the soil. The cutters by their 
rotary action first enter the soil, making a semicircular trench, 
which during the progress of the machine is constantly preserved 
at the required depth ; and the soil, abraded and cut down as the 
machine advances, is thrown off tangentially behind, and depo- 
sited in a comminuted, inverted and aerated condition. The 
machine is mounted on two pairs of very broad wheels or rollers, 
the pair used for propelling being made with ribs across the 
periphery, to ensure a sufficient bite or hold upon the ground. 
Of course, a rapidly revolving grating-cylinder could exert but a 
trifling propulsive action ; and the power required to cut up a 
stratum of firm soil into earth-sawdust is enormous, so that with 
any ordinary steam engine, the operation would be tediously slow 
and exceedingly costly. One of the most carefully studied but 
the earliest of steam rasping or scratching machines, is calculated 
(accortling to the inventor's " specification") to advance, with a 
very powerful engine, about 200 lineal yards per hour ; so that a 
width of even 3 yards would not accomplish more than \ \ acres 
a day. And the first machine of Mr. Komaine, which from its 
high velocity minced and powdered the soil, was found to demand 
far greater motive power than could be feasibly applied ; the 
conclusion from the experiments being that sucli a material as 
the land must be dealt with in masses larger than mere dust, 
and must be cut and raised by a slow steady motion. It is quite 
true that the efficacy of a manure greatly depends upon the 
extent to which it is amalgamated with a pulverized soil. Dr. 
Voelcker says, " On clay land superphosphates arc of no use 
unless the land be properly pulverized. Some farmers imagine 
that by using the best artificial manures they do not require so 
much labour, or any additional labour. There can be no greater 
mistake ; for the best artificial manures often fail, more or less 
entirely, for want of proper pulverisation of the soil. It is of 
the greatest consequence that the land on which artificial manures 
are used, sliould be in a high state of subdivision." And the 
evidence of all afjriculture and horticulture combined, fortifies 
the Tullian principle and Lois Wcedcm practice of gaining 
fertility by moans of a fine mould that infinitely multiplies the 
absorptive superficies of the acquisitive earth. But tlie indis- 
pensable value of a comminuted seed-bed, and the utility of a 
