552 REPORT — 1880. 



Buppression are immediate ; on wheat they are manifested a little more slowly, but 

 are still very signiticaot, and when magnesia is excluded- from the soil the yield 

 falls to ahout 123 grains instead of 337. 



' The suppression of the lime produces a less sensible effect — the yield is then 

 ahout 307 instead of 337. 



' Leaving the culture in calcined sand, I extended my investigations to various 

 natural soils. 



' On submitting them to the same experimental system we found that .... 

 the yield is mamtained at the same level as when sulphur, silica, soda, magnesia, 

 iron, and chlorine are added, which explains to jou why I did not go further into 

 the effects of those bodies. 



'Experience, therefore, shows that the four ingredients — nitrogenous matter, 

 phosphate, potash, and lime — ai'e the onlv ones that need be admitted into manures.' 

 (ViUe, pp. 153-5.) 



'I give the name, therefore, of normal manure to the mixture of phosphate of 

 lime, potasTi, lime, and a nitrogenous material. 



' In so doing, I do not intend to deny the utility of the other ingredients ; I 

 exclude them from the manure because the soil is provided with them naturally. 



' If we pass from these fundamental data to the function of each mineral 

 ingredient in particular, the results are neither less expressive or less explicit. The 

 soil being provided with nitrogenous matter as a constant ingredient : — 



M. Ville's conclusions respecting magnesia, and indeed silica, appear to me to be 

 far from con^"incing. If the above results can be said to demonstrate anything, thej' 

 demonstrate that magnesia comes next to phosphate in importance as an element of 

 mineral manures, and, as I shall show eventually, this is not far from the truth. I 

 shall, however, now proceed to show that there are experiments recorded indicating 

 that considerable advantage is derived by adding to very many soils more magnesia 

 than they naturally contain, and we shall find also important testimony to its value 

 where it naturally occurs. 



Sir Humphry Davy in opposing the common notion of the noxious qualities of 

 magnesian lime, and accounting for this prevalent and erroneous opiniop, states 

 that:— 



' Magnesia in its mild state, t.e. fully combined with carbonic acid, seems to me 

 to be always a useful constituent of soils. I have thrown carbonate of magnesia 

 upon grass, and upon growing wheat and barley, so as to render the surface white, 

 but the vegetation was not injured in the slightest degi-ee ; and one of the most 

 fertile parts of Cornwall — the Lizard — is a district in which the soil contains mild 

 magnesian earth. The Lizard Downs have a short and green grass which feeds 

 sheep, producing excellent mutton, and the cultivated parts are amongst the best 

 of corn lands in the country.' (' Davy's Agri. Chem.' pp. 299-300.) 



Davy also found that wheat grew better in a soil with which he had mixed 

 peat and magnesia than in either the 'pure soil,' or the pure soil and peat alone. 

 It grew very well in the pure soil, and nearly as well as with magnesia in the 

 mixture of peat and pure soil, but peat often contains a notable quantity of 

 magnesia. The ashes .of the brown herbaceous peat in the neighbourhood of Troyea 

 contain 14 per cent, of magnesia, and those of a peat from the frontiers of Bavaria 

 and Bohemia contain 3'5 per cent of it. Gelatinous silica and sulphate of lime are 

 also frequent constituents of peat, and the fact, therefore, that the mixture of peat 



