lOG 
Report oil the Farming of (lie 
remedy the defect which then threatened and still threatens the 
integrity of the four-course system, viz. the liability of clover- 
seeds to fail if sown so frequently as once in four years. 
To whatever cause this phenomenon may be attributed, — whether 
it arises from an exhaustion of the mineral constituents of the soil 
by the plant itself; whether from excretion by its roots, as French 
chemists have said ; or whether, as contended for by Mr. Thorp, 
it is always killed by frost, and this in proportion to the want of 
cohesiveness of the soil, occasioned by the too frequent growth of 
it ; — whether these or any mysterious laws of vegetable life be the 
causes of its failure, the remedies that have been hitherto applied 
have proved insufficient. 
With respect to the exhaustion of the food of the plant. Pro- 
fessor Liebig has asserted — and his assertion is confirmed by the 
experience of practical men — that, " where the intervals at which 
the same plants can be cultivated with advantage are very long, 
the time cannot be shortened even by the use of most powerful 
manures." The excrementitious theory, we believe, has been 
given up. Indeed, even if this theory had been ever fairly esta- 
blished, yet its supporters do not appear to have ever suggested a 
counter-agent. 
Then as to the remaining reason assigned by Mr. Thorp for 
the failure of the clovers, viz. that they are killed by frost, it can 
only be affirmed that the best Wold farmers — men upon whose 
judgment and accuracy the greatest reliance can be placed — have 
followed Mr. Thorp's advice most implicitly ; have endeavoured 
to obtain compactness of the soil in the way he recommends ; 
have pressed their land when sowing it with wheat ; have rolled it 
with Crosskill's clod-crusher immediately after sowing, and again 
in March ; have rolled the clover-seeds in autumn with a smooth 
iron roller, have covered them with a good dressing of fold-yard 
manure, and have avoided autumnal eatage ; and yet, after all 
these precautions, they have found that the plant, though looking 
pretty well during autumn and even winter, has dwindled very 
much away ere the month of April arrives ; and thus they have 
been compelled to relinquish the quadrennial growth of it, and to 
endeavour to find a substitute. All substitutes, however, hitherto 
tried have proved of inferior value. Of these, tares have occasion- 
ally been adopted on the Wolds as a sheep pasture. Compared with 
clover, however, they afford a scanty herbage. In wet weather 
the trampling of sheep is injurious to them ; but the chief evil is 
that on these soils they are found to be prejudicial to the suc- 
ceeding corn-crop. Rape has been substituted for clover on the 
deep Wolds : and it was noticed by Mr. Strickland that a better 
crop of wheat was produced here after rape than by any other 
course. But in the spring and early summer, when sheep-meat 
