General Notices. 325 



containing but little or no calcareous matter. To suppose, agreeably to the 

 theory of Sir Humphry Davy, that carbonate of lime operates only by 

 giving a proper texture to the soil, and furnishing plants with an ingredient 

 necessary to their structure, is, to say the least, attributing a seemingly small 

 power to such disproportionate means, if it be considered that, to all appearance, 

 every purpose of a substance so inert, according to this theory, might be answered 

 equally well by a particular combination of the other earths : and if Hornby's 

 dissertation be looked to for a solution of the wonder-working power of this 

 mineral, the answer there given, that it supplies by its decomposition in the 

 plant, as vegetable food, the carbonic acid which it retained, is not only un- 

 satisfactory, but at variance with the assertion of Sir H. Davy, that the lime 

 found in plants is usually in its carbonated state. The mechanical, action of 

 lime insisted upon by the first-named gentleman seems insufficient to robe the 

 coarse brown turf with a coat of the richest green, and the chemical operation 

 of the other gentleman accounts but ill for the uncultivated grasses and plants 

 giving place to a sweet herbage wherever lime has been applied. 



My purpose of addressing you, however, is not to find fault with former 

 theories on the subject of lime (that were an easy task), but to offer, with 

 all humility, a new one to your consideration. It is well known to chemists, 

 and also to many other persons, that carbonate of lime has the power of 

 creating nitrate of lime by its combination with the nitrogen of the atmo- 

 sphere, and also with that escaping from decomposing animal and vegetable 

 matter. That this saline substance enters into, ,and is of use in, the 

 constitution of plants, there is every reason to believe, and, that it under 

 goes decomposition there, I can have but little doubt, notwithstanding the 

 author of Lectures on Agricultural Chemistry, holds an opinion unfavourable 

 to the decomposition of alkaline substances. M. Th. de Saussure's Re- 

 searches on Vegetation furnish something like a proof of a change taking 

 place in saline matter, after its absorption by plants. That philosopher states 

 that 100 parts of ashes from wheat, in flower, yielded him 43*25 of soluble 

 salts, whilst the same quantity of ashes from wheat, the seeds being ripe, 

 produced only 11 parts; and he gives also another analysis of the same 

 vegetable in like states, and also a month before flowering, the result of which 

 answers almost precisely to the former one, in the point upon which my 

 opinion of a change is grounded, saving that in the ashes of the wheat cut a 

 month before flowering there were found 60 parts of salts ; a circumstance 

 still more in favour of that opinion. Thus it appears that wheat in a green 

 state possesses more salts than when dry, and we may conclude that most 

 other vegetables agree with it in that particular ; indeed, the analysis of some 

 other plants by M. Th. de Saussure gave results that would strengthen the 

 propriety of such a conclusion. Such being the case, what other inference can 

 be drawn, but that decomposition generally takes place in saline matter after 

 its entrance into plants ? Supposing me, then, to have established what I aimed 

 at proving, the next question to be considered will be, how nitrate of lime can 

 be serviceable to growing vegetables. My answer is, that most probably 

 nitrate of lime offers to the plant a substance better than all others, by its 

 ready solution, for lime being absorbed into its system j and it may not be 

 impossible that its decomposition should furnish nitrogen for the production 

 of gluten and albumen, since those substances are found more especially in 

 plants delighting in a calcareous soil, such as wheat, clover, saintfoin, &c. If 

 this argument in support of the utility of nitrate of lime in vegetation be one 

 founded on true principles, by a parity of reasoning considerable light may be 

 thrown on the doctrine of paring and burning, as the ashes arising from that 

 operation might yield salts answering at least to that substance in having 

 nitrogen in their composition, and might thereby furnish an essential element 

 for the production of albumen in the particular plants possessing that matter. 

 Agriculturists are well aware that a peaty soil, except it be pared and burned, 

 will not produce good crops of grain, but that,when the ashes yielded by burning 

 are employed, an average produce of oats, if not of other grain, may be expected : 



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