27 4 ^'^ afcertainhig the ^lalliy of Limejlone, Aug, 



cannot prefume to give any opinion refpe£\ing the proper quanti- 

 ty of either which ought to be ufed, according to their diiFerent 

 •quahties. I may venture however to aflert, that it is better to 

 repeat fmall dofes of either, than to truil to one's judgement for 

 afcertaining the full dofe which in any cafe may be thought necef- 

 fary. 



It may alfo occur to A. S., tliat the impurity of his acid is of 

 little confcquencc, when ufed in the procefs I have propofed to 

 farmers, as the lofs of weight only is to be noticed. By ufing 

 impure acid, it is more apt to fly off in fumes, than that which 

 is pure, during the extrication of the fixed air ; and the extrication 

 cannot be properly effecled without the acid being greatly diluted, 

 which occafions the menjlrua to acquire an inconvenient bulk. 



I am, Sir, your mod obedient and humble fervant, 



George S. Mackenzie. 



Couly loth April 1804. 



TO THE CONDUCTOR OF THE FARMER'S MAGAZINE. 



On afcertaining the ^ality of Limeflone, 

 Sir, 



The benefits that might be derived from the union of chemical 

 knowledge with extenfive obfervation of agricultural facts, are 

 perhaps incalculable. Your correfpondent A. S. has, in the 

 Number for February, given a method of afcertaining the quality 

 cf lime, which, however, only regards the quantity of foluble 

 matter in a given weight of lime or limeftone. He concludes, 

 * that the limeftone which leaves leaft fediment when diffolved, 

 is of courfe the beft ; ' I fuppofe him to mean, for the pur- 

 pofcs of agriculture. It is impoflible to lay down any general 

 rules refpeding the fitnef. of lime for the purpofesof agriculture, 

 becaufe much muft depend on the peculiarities of foil, and other 

 circumftances. All that can be accomplilhed by chemical means, 

 is to afcertain tlie degree of purity of the lime, and to infer, from 

 that, to what kind of foil it is belt adapted. 



There is one earth, however, lately found In feveral limeftones, 

 which is highly injurious to the vegetation of plants, and is not 

 difcoverable by lolution merely, being, equally with lime, foluble 

 in muriatic acid. This earth is magnefra, which Mr Tennant, 

 the gentleman to whom we owj this fa61:, has, by direct experi- 

 ments, proved to ])e extremely noxious to plants. The prefence 

 of mijgiiefia in lime, is found to be a very common occurrence, 



Th-^^ 



