154 



Magnesian Lime. 



Vol. VII. 



For the Farmers' Cabinet. 



Magnesian Lime. 



Messrs. Editors, — Your correspondent, 

 B. Webb, throughout his ingenious essay 

 which appeared in the last number of the 

 Cabinet, has wholly overlooked or mistaken 

 the objects I had in view, in the essays on 

 magnesian lime. He has set up a target of 

 his own manufacturing, at which to let fly 

 his arguments. The real question at issue, 

 is not whether magnesia or sand is useful as 

 manure, or whether any farmer would buy 

 sand or magnesia, instead of lime, at the 

 same price, if he had his choice. At least I 

 never made such an issue, and shall not 

 therefore undertake to defend the side he 

 has assigned to me in the discussion of it. 

 I have never undertaken to show, that mag- 

 nesia is of itself useful as a manure. I have 

 never even said that magnesian lime was su- 

 perior to pure lime as a manure. I only 

 ventured to make some suggestions on this 

 point, as interesting and important subjects of 

 inquiry to the practical farmer, and to which 

 I intend again to direct his attention. 



The doctrine of Tenant and his followers, 

 it is well known is, that " magnesian lime, 

 (not magnesia,) is exceedingly injurious to 

 vegetation." Now, in opposition to this I 

 did say, and again repeat the offence, if it is 

 one, that the whole experience of the farm- 

 ers of South-eastern Pennsylvania, is dia- 

 metrically opposed to this doctrine; and that 

 whatever improvement they owe to lime, it 

 is to magnesian lime and to no other. I 

 mean, however, only to speak in general 

 terms; — I do not assert there is no limestone 

 in that part of the country free from mag- 

 nesia, or containing only a small portion of 

 it. What I assert is, that the lime has been 

 there generally used, without any knowledge 

 whether it contained magnesia or not, and 

 without any such perceptible difference in 

 the effects of different parcels, as to induce 

 the farmers to quit one kind and adhere to 

 the other. And further, that some of the 

 quarries, the lime from which has long been 

 held in high estimation for agricultural pur- 

 poses, have been found upon analysis to be 

 highly impregnated with magnesia. Are 

 these facts or not] 



If your readers will turn to the essays I 

 have heretofore sent you on this subject, I 

 think they will labour under no misappre- 

 hension as to the issue I have made. I have 

 again and again stated it as a fact, that mag- 

 nesian lime has proved highly beneficial to 

 the agriculture of South-eastern Pennsyl- 

 vania, and challenged contradiction, if it be 

 not so. And who has controverted if? Not 

 any one. Even your correspondent admits it ; 



for he says, " no one has ever denied it, — no 

 one has even insinuated that magnesian lime 

 is not beneficial to the soil." Now, here 

 one would suppose the controversy ought to 

 end, for this position is all I ever really con- 

 tended for. But Mr. Webb has entered into 

 a long investigation and argument, to show 

 that magnesia is deleterious, or at least val- 

 ueless as a manure ; and that if magnesian 

 lime has proved beneficial, it was owing to 

 the lime it contained, — the good effects of 

 which were more than sufficient to counter- 

 act the bad effects of the magnesia, and that 

 in no case can we expect that a mixture of 

 lime with foreign substances will be equal 

 in value to lime in a pure state. The fair 

 inference from which I presume is, that 

 magnesia and other foreign substances, if 

 not actually deleterious, when combined with 

 lime, must at least be inert and valueless; 

 and consequently, that the quantity used, 

 must be increased in the proportion at least 

 of the foreign matter contained in it, to pro- 

 duce the desired effects. But is this the fact 

 so far as relates to magnesian lime] In that 

 part of the country where this kind of lime 

 has been longest in use, I believe 60 bushels 

 are considered about an average dressing for 

 an acre of land, and from such dressings 

 very beneficial effects have been derived ; 

 while of mild or pure lime, from 50 to 200 

 bushels are considered as a moderate dressing, 

 and as much as 500 or 600 bushels have 

 sometimes been spread on an acre with ad- 

 vantage, at least so say the books. Now, the 

 natural inquiry is, does this increased quan- 

 tity of pure lime produce increased benefi- 

 cial effects over the limited quantity of the 

 magnesian] Will an acre of land dressed 

 with 600 bushels of pure lime, yield ten 

 times as great an increase of crops, as one 

 dressed with 60 bushels of magnesian lime 1 

 This is the only point, as I conceive, now at 

 issue between us, which is at all likely to 

 interest the farmer ; and it is one that has 

 hitherto been pretty much evaded or over- 

 looked by the advocates of the superiority of 

 pure lime. 



The experience of the farmers of South- 

 eastern Pennsylvania, continued through a 

 long course of years, and spread over a wide 

 district of country, containing a great variety 

 of soils, having fully established the fact, 

 that magnesian lime is not necessarily dele- 

 terious to vegetation, but that the Pennsyl- 

 vania variety of it at least is highly beneficial, 

 the next most material point to be investiga- 

 ted is, what is its economical value for the pur- 

 poses of the farmer, in comparison with pure 

 lime. Is it more or less costly, to use in pro- 

 portion to the good effect produced ] 



To procure pure lime in sufficient quanti- 



