430 



FARMERS' REGISTER— MAGNESIA. 



lustratethis position, by stating two cases in point, 

 ■which fell under my own observation. 



In the neighborhood of Sterling, soils arc dis- 

 tinguished into carsc and dryfidd. The carse is a 

 tenacious alluvial clay, which occupies the exten- 

 sive plain through which the Forth performs 

 his whimsical meanders. It had been an im- 

 memorial practice to lay great doses of lime on 

 this soil ; but my flither Avas the first person, in the 

 district north-west from Sterling, who ventured 

 to put lime on dry field land. PI is soil had been 

 mostly formed from the decomposition of red and 

 brown sandstone, and was a friable loam inclining 

 to sand, and in some cases to gravel. A field be- 

 ing fallowed, and put in good order, the lime- 

 shells were dropped over it in heaps ; and, after 

 they had slacked in the air, the lime was spread 

 over the surface with spades. The same quantity 

 was applied, and the same mode of application 

 was adopted, that had long been practised in the 

 carse lands. Wheat was sown; but except in a 

 few spots, which had escaped an excessive dose oi 

 lime, none grew. It was long before this field 

 recovered its fertility ; and the bottoms of the 

 heaps remained steril during many years. The 

 opinion of the people there, that lime would de- 

 stroy dryfield land, was completely confirmed. 

 But the fiiilurc of his first experiment had no ef- 

 fect upon my father. In his future operations, he 

 slacked his shells beside a pool of water, and then 

 spread the powder equably, and in moderate 

 quantity, fi'om carts. The eliects were both 

 striking and highly beneficial. 



The other case occurred in Lanarkshire. A flat 

 piece of land, consisting of what farmers call a 

 cold till, being mostly formed from the decompo- 

 sition of blaes, and other clay strata which usually 

 accompany coal, was contiguous to a risuig 

 ground, consisting of what farmers would call a 

 sharp turnip soil, in some places shallow, and in- 

 cumbent on red and brown sandstone. About 

 two thirds of each of these pieces of ground had 

 been limed on the sward, while in pasture in the 

 heap way, already described. The remainder of 

 both was limed, by spreading the powder from 

 shovels. They were both ploughed at the same 

 time and sowed with oats. Where the lime heaps 

 had stood on the till soil, the crop grew with the 

 utmost luxuriance, and continued green after other 

 parts of tlie field were ripened; but where the 

 heaps had stood, or an excessive dose had been 

 applied to the other soil, nothing grew at all ; and 

 this distinction remained clearly marked, not only 

 while the fields remained in crop, but even after 

 they were thrown into grass ancl pasture. The 

 parts lined by shovels, exhibited an equable fer- 

 tility, though greatest in the till soil where most 

 lime had been applied, and diminished in the other, 

 where more than a certain quantity had been 

 used. 



This limestone contained a small portion of mag- 

 nesia, though not apprehending any evil from it, 

 I was at no pains to ascertain its proportion. 



It is not stated that any bad consequences re- 

 sulted from applying the magnesian limestone of 

 Doncaster in moderate quantities; but the contra- 

 ry. In the cases I have stated, it appears evident, 

 that the opposite effects of the lime did not arise 

 from magnesia, or any poisonous ingredients what- 

 ever in its composition. The effects can only be 

 ascribed to the opposite qualities of the soils ; one 



requiring a very large dose, and the other being 

 only capalile of melioration from a very moderate 

 one. In short, what added great fertility to the 

 one soil, was found utterly to destroy the fertility 

 of the other. I am therefore inclined to think, that 

 the pernicious effects of the Doncaster lime are 

 not to be ascribed to magnesia, but to the quality 

 of the soil to which it was applied, which rendered 

 it incapable of receiving a large dose. But as I 

 mean to show, positively, that magnesia, instead 

 of being a poison, is a food of plants; to account 

 f()r all the facts stated by your correspondent, I am 

 inclined to admit, that an overdose of this sub- 

 stance may prove more injurious to certain soils 

 than an overdose of lime. Magnesia, and lime, 

 and indeed any of the primitive earths, are known 

 to be, of themselves, the most infertile of all soils. 

 Though no soil is fertile without lime, its excess 

 produces sterility ; and the most fertile soil is 

 formed from a variety of the primitive earths, 

 combined in certain proportions, yet unknown. 

 It is extremely ])robable that a certain proportion 

 of magnesia, as well as of lime, contributes to the 

 fertility of soils ; though there may be some soils 

 which an overdose of magnesia may more readily 

 injure than an overdose of lime. From this sup- 

 position, I am disposed to account for the fact, 

 stated p. 150, that lime, which contained two parts 

 of magnesia to three of lime, proved injurious, 

 w hile an equal quantity of pure lime proved be- 

 neficial : not that the magnesia Avas hurtful in it- 

 self, but that the soil might have been previously 

 saturated with it, so that a new addition proved 

 hurtful. In all cases of this sort, the nature and 

 qualities of the soil should be examined and stated, 

 as well as of the substances applied to it. From 

 the fiicts I have stated, it might as rationally be in- 

 ferred that lime, as that magnesia, was a poison to 

 plants, when applied to certain soils. There are 

 certainly soils where an overdose of lime will 

 prove as injurious as an overdose of magnesia. 



But that magnesia, so far from being a poison, 

 is a pabulum of plants, or promotes their growth, 

 in addition to the facts adduced in the paper which 

 forms the sulyects of your correspondent's criti- 

 cism, may farther appear from this circumstance — 

 that the refuse of magnesian works, in this part of 

 the country, is eagerly sought for and applied as 

 manure. Are we to suppose farmeis so blind and 

 stupid, as to persevere in applying poison to their 

 crops, in place of nutriment.'^ 



If any doubt is entertained respecting the accu- 

 racy of the experiments alluded to in my former 

 communication, I shall proceed to detail them in 

 the author's own words. 'J'hey were made by 

 Andrew Steele, Esq. W. S. at the time the alarm 

 about magnesia was at its height, and had found 

 its way into your useful work. 



' On 26th April 1801, I sowed two pots, con- 

 taining the 



1st, yV magnesia, the rest earth. 

 2d, yV lime, the rest earth. 



'The plants in the pot containing magnesia, I 

 find recorded in my book of experiments, throve 

 better than those in that which contained the lime. 



' This might arise from souie particular and im- 

 perceptible circumstances; but I esteenied it suf- 

 ficient for my purpose to have ascertained, that 

 magnesia is neither poisonous to the seeds, nor ob- 

 structs the growth of grain. 



' The same year I tried magnesia spread on the 



