DAMAGE TO CROPS BY MARLING. 425 



from insects, among the roots. All the land marled from pits Nos. 

 7 and 9 (both yellow) from 1820 to 1822, is so much diseased as 

 to promise not more than half a crop. The corn is twice as large 

 as on the spaces left for experiment without marl, yet looks much 

 worse } though three weeks ago its superiority in colour and vigour 

 was even more than in size. With but few exceptions, the land 

 newly marled from the same pits, and the old marling from Nos. 1 

 and 8 (both blue), as well as that not marled, are free from this 

 disease. The parts most affected are those which were driest and 

 poorest, and of course were least covered with vegetable matter. 

 Yet though the corn on this old marling is generally so bad, it is 

 yet evident that the land is more benefited by the manure than at 

 first. Flourishing stalks of corn, 18 to 24 inches high, are seen fre- 

 quently within a few feet of those most hurt by this disease." 



Subsequently, when the whole extent of injury could be seen, 

 the following remarks were written in' the journal, at the date 

 below. 



t( October 15th. The damage caused by marl to this crop I sup- 

 pose to be about one-third of what the land would otherwise have 

 made, judging from the present and former measurements of the 

 same land, where experiments were made. 



" Nearly all the heavy marling in Finnies (at 800 bushels), about 

 20 acres,* suffered by it; the poorest and lightest most injured, 

 here and in Court-House field. The few rich spots escaped, as did 

 most of the piece plastered (on the heavy marling) in 1820. The 

 marks of this experiment were destroyed, and the superiority was 

 not so regular as to enable me to trace the outlines of the gypseous 

 earth but an acre of corn might be taken which certainly was 

 plastered, better than any other acre in the old land. This at least 

 proves that gypsum contained [if any] in the marl has not caused 

 the disease. The poor land, lightly marled in 1819, showed but 

 little of the disease, and none was found in the piece not marled, 

 nor in any marled since the last crop [or now first cultivated since 

 being marled.] ' 



"In Court-House field the injury was confined to 19 acres, the 

 poorest part of the field, which was in corn in 1821,"j" marled and 

 fallowed 1822, and in wheat 1823, corn 1824. The remainder of 

 the old land, which had not been cropped so severely, and was 

 covered as heavily with blue marl, brought a fine crop, quite free 

 from the disease. The new ground was mostly marled very heavy 

 (800 bushels of 45 per cent.),J and this and all my former clear- 

 ings (some marled equally heavy) were also quite free. These 



* See Exp. 10, p. 132, Essay on Cal. Man. 



f Exp. 11, p. 185. 



J Exp. 1 to 4, "pp. 117 to 121. 



36* 



