the Progress of English Agriculture. 815 = 549 
I. Whether or not clays are usefully burnt, and used in that 
s e as manure ? 
. Whether or not land will be improved by liming? 
. Whether it is better to apply lime, or marl, or clay, on a 
p ticular soil ? 
1. Whether special manures, such as superphosphate or am- 
niiacal salts, can be used (of course discreetly) without per- 
niently injuring the land ; or whether the farmer should rather 
d end upon the liberal application of farmyard manure, that 
h may restore to the land all the elements of fertility removed 
ii he crops ? 
. What kinds of artificial manures are best suited to soils of 
v; ous composition ? 
he investigations of Messrs. Lawes and Gilbert in rela- Influence of ex- 
ti to the exhaustion of land by continuously ffrown corn- periments on 
... . . . , . p ° . , modern culti- 
a)s, their inquiries into the distribution oi nitrogen in the yation. 
lal, and the examination of land-drainage by these gentlemen, 
b Tiyself, and by Dr. Frankland, as well as other investigations 
01 he unexhausted elements of manure left in the land by the 
ccjumption of purchased food, or the use of various artificial 
miures, have all had a powerful influence on improved systems 
ofiodern cultivation. 
caving out of consideration all questions of tidy or slovenly Permanent fer- 
miagement — such as those connected with draining, fencing, ^'^'*y 
wding, &c. — whereby the standard of productiveness may be 
loBred, and making allowance for variations in the average 
pi luce of the land, due to the character of the seasons, 
.\1 Lawes was the first man to point out that all land, left 
ui lanured for a longer or shorter number of years, has a certain 
♦ (lard of natural produce, practically speaking, varying within 
in limits according to the character of the season, and bad 
>od management, which standard of natural produce on a 
■ scale could practically be neither permanently increased, 
Jic materially reduced by cultivation. 
e further explained what is the real meaning of land " out 
mdition " and land " in good condition," by showing that 
latter is an acquired fertility, due to the application of 
ure ; and that the former is the result of exhaustion of the 
miures, which temporarily raised the fertility of the land, in 
th production of two or more crops, or in loss by drainage 
an other causes, and the return of the land to its natural 
'^^titlard of productiveness. It is well, however, to bear in 
I that Mr. Lawes' observations respecting permanent and 
)orary fertility apply to actual English farm-practice, and 
the term permanent fertility must not be pushed to an 
me signification. 
)L. XIV.— IS. S. 3 I 
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