206 On Lime and Marls* 



part of a field which I saw. He said its effects were si- 

 milar to dung, giving out its strength to the first crop, 

 but that they were soon exhausted. Perhaps if he had 

 put on two or three hundred bushels to the acre, in- 

 stead of sixty, they might have lasted longer, tor though 

 the lime he used is considered of very little value, it 

 may possibly be considerably stronger than that of 

 which Dr. Anderson put ^even hundred bushels. But 

 if our farmers in Pennsylvania, had no other lime ex- 

 cept such as would require three hundred bushels per 

 acre, I presume very little would be used for manure, 

 for this plain reason, that they could buy as much land 

 for the money, as the lime would cost. 



Dr. Anderson sets it down as a fixed principle, 

 ^' that there is only one kind of calcareous matter ; and 

 '' that all the varieties of calcareous substances we 

 '' meet with, are entirely occasioned by a diversity in 

 '' the nature of the extraneous bodies with which the 

 '' calcareous matters are wnited, or a difference in the 

 '' form it may appear in at the time." If this is the 

 case, the enquiry should be, whether the most pure 

 and unmixed calcareous substances, or those which 

 we find in combination with other matters, are the 

 most valuable, either as a cement or for manure. The 

 most pure calcareous substances which we know, are 

 chalk, pulverized shell, and the most pure shell marl. 

 For a cement it is well known, that these three varie- 

 ties are of little or no value ; and as a manure they re- 

 quire a great quantity to produce any effect. The most 

 pure shell marl, which will be found to contain less 

 extraneous matter than any stone lime, requires at least 

 forty loads to an acre, and, sometimes, from one hun- 



