LIMING. 305 



it is in concurrence with organic manures that it becomes truly use- 

 ful ; it is nowise, and never can become, a substitute for these. 



The geological constitution of a country is perhaps the best guide 

 10 the necessity or advantages of liming. Soils that are derived 

 from pluionic or igneous rocks, in which felspar, mica, or quartz 

 predominate, are on the face of things likely to be improved by the 

 introduction of lime. Direct analysis would of course give more 

 decisive information on the fact. In any case, the measure recom- 

 mended by prudence is to make a few preliminary trials upon the 

 small scale ; the experimental method is the only safe one in agri- 

 culture, when the question is in regard to the adoption of new plans. 

 In England it is customary in liming clayey lands to allow from 

 230 to 300 or 310 bushels of stimulant per acre ; on lighter soils 

 the dose may vary from about 150 to 200 bushels, according to their 

 character. In France the quantity usually employed is greatly less, 

 from about 60 to 70 bushels being all that is generally thought ad- 

 visable, and this at intervals of seven or eight years. In the neigh- 

 borhood of Lisle little use is made of lime, although there the land 

 is generally any thing but calcareous ; perhaps the want of lime is 

 not felt in consequence of the universal practice of employing the 

 Flemish manure, which, as we have seen, contains ammoniacal 

 salts, (and both human urine and excrement contain a large quantity 

 of phosphate of lime and phosphate of magnesia in addition, the 

 very salts that the generality of vegetables crave.) In the vicinity 

 of Dunkirk, however, lime is frequently applied in the dose of be- 

 tween 40 and 50 bushels per acre, and with effects that are said to 

 continue for ten or twelve years. 



The dose of lime introduced into the soil in different countries, is 

 moreover in a certain relation with the time during which the action 

 of the earth is believed to continue ; as the quantity administered at 

 once is small, the dose must be repeated more frequently. Near 

 Dunkirk they use from 40 to 50 bushels per acre every 10 or 12 

 years ; in the department of La Sarthe, according to M. Puvis, they 

 scatter on some 9 or 10 bushels only ; but they do so every three 

 years. This would lead us to conclude that soils which really 

 wanted lime should receive a dose in the proportion of about 3| 

 bushels per acre annually. But the crops gathered from the ground 

 every year, certainly do not abstract any thing like this quantity of 

 calcareous matter ; which would induce us to infer, that after a cer- 

 tain time the land will contain such a quantity of lime as to make 

 any further addition of it unnecessary, or at all events, unnecessary 

 save at rare and distant intervals. 



One of the great advantages which lime has over all the other 

 forms or kinds of calcareous stimulants employed, is unquestionably 

 the state of extreme subdivision which it acquires in the quenching. 

 In the course of falling down into this extremely fine powder, lime, 

 as has been said, combines with a large quantity of water. But the 

 change experienced does not stop short here ; the air always contains 

 some lOjOOOths of carbonic acid gas, for which the hydrate of lime 

 has a powerful affinity, so that it absorbs this gas greedily, aban- 



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