2.)8 On the .Mollifications of the Four-Courso Rotation, S^-c. 
3rd. Tliat a ewe flock leaves a jjood profit when well managed, 
with a liberal allowance made lor keep at received rates, 
4th. That a dry flock may be kept without loss, or with a 
moderate profit, according to the season, if the turnips consumed 
be valued at 6s. 8c?. per ton. 
XV. — On the Modifications of the Four-course Rotation, which 
JModern Lnprovenients have rendered advisable. By P. Debell. 
TUCKETT. 
The object of a rotation of crops is two-fold. 1st. To alternate 
with the narrow-leaved cereals those plants which, from their 
producing a large surface of foliage, are especially fitted to 
extract from the air the carbon, oxygen, and hydrogen, needed 
for the formation of the organic portions of all our crops. 
2dly. By recurring to the same crop only at more or less extended 
intervals, to avoid the exhaustion of those various inorganic 
matters in the soil which are required by our crops in very 
different proportions, and for the supjily of which Ave have to 
trust partly to the soil itself, and partly to the manures which 
we apply to it. 
The Norfolk four-covirse rotation, as originally introduced^ 
consisted of — 
111 the first j^ear 'J'nmips. 
second }-ear .. .. Harlcy. 
,, third year .. .. Clover. 
I'ourth year .. .. AMieat. 
and nothlnfj could be better adapted to the first of the above 
objects. The broad leaves of the turnip and the rich foliage of 
the red clover, olitain from the air a vast quantity of vegetable 
matter, which, if the crops are consumed on the land, or returned 
to it in the shape of manure, remains for the production of suc- 
ceeding crops. 
But experience has proved that a greater variety of cropping 
is desirable, and that one, if not more, of those crops cannot be 
successfully grown so often as once in every four years. 
In considering the modifications that are thus rendered advis- 
able, it is proposed first, to notice such variations of the four- 
course shift, as retain its main feature— a fallow or root-crop once 
in four years ; and afterwards to proceed to other courses, such as 
the five and six course rotations. 
The great difficulty in the Norfolk four-course rotation, is the 
failure of the clover plant. If sown every four years, especially 
on light soils, the land becomes clover-sick, and the clover 
misses plant. Hence the first and now universal modification, 
