158 DISEASED CROPS CAUSED BY MARLING. 



men 4, page 60), produce indeed a pale feeble growth of corn, 

 such as might be expected from poor gravelly soils ; but whether 

 the plants yield grain, or are barren, they show. none of those pecu- 

 liar and strongly marked symptoms of disease which have been 

 described. Some such places on my farm, from which great quan- 

 tities of poor sandy marl had been removed for manure, and where 

 the remainder still was of unknown depth, have been afterwards 

 cultivated with the surrounding land ; and with no more aid than 

 the portion of the adjacent soil carried thereto necessarily by the 

 plough, these places have gradually improved to a product equal to 

 12 or 15 bushels of corn per acre, and have never exhibited any 

 mark of the marl disease. 



By calculation, it appears that the heaviest dressing causing in- 

 jurious consequences, if mixed to the depth of five inches, has not 

 given to the soil a proportion of calcareous earth equal to two per 

 cent. This proportion is greatly exceeded in our best shelly land, 

 and no such disease is found there, even when the rich mould is 

 nearly all washed away, and the shells mostly left. [Soils of re- 

 markable fertility from the prairies of Alabama and Mississippi 

 have been shown (page 66) to contain from 8 to 16 per cent, of 

 calcareous earth, all of which proportions were in the state of most 

 minute division, and therefore most ready to produce this disease, 

 if it could have been produced by the quantity of this ingredient. 

 A specimen of soil remarkable for its great fertility, and maintaining 

 it under 40 years of successive corn culture, in Scioto valley, Ohio, 

 was sent me by Dr. Thomas Massie. It contained 10 per cent, of 

 carbonate of lime and magnesia. The soil of the borders of the 

 Nile", celebrated for its exuberant fertility through thousands of 

 successive crops, contains about 25 per cent, of carbonate of lime, 

 (LyelTs Geology.'}'] Very fertile soils in France and England 

 sometimes contain 20 or 80 per cent. Among the soils of remarka- 

 ble good qualities analyzed by Davy, one is stated to contain about 

 28 per cent., and another, which was eight-ninths of silicious sand, 

 contained nearly 10 per cent, of calcareous earth. Nor does he 

 intimate that such proportions are very rare. Similar results have 

 been stated, from analyses reported by Kirwan, Young, Bergman, 

 and Rozier (page 51) ; and from all the same deduction is inevita- 

 ble, that much larger natural proportions of calcareous earth, than 

 our diseased lands have received, are very common in France and 

 England, without any such effect being produced. 



From the numerous facts of which these are examples, it is cer- 

 tain that calcareous earth acting alone, or directly, has not caused 

 this injury ; and it seems most probable that the cause is some new 

 combination of lime formed in acid soils only ; and that this new 

 combination is hurtful to grain under certain circumstances, which 



