Review of Essays on Calcareous Manures. 151 





lime which might be applied ; but this is exactly the reverse of what 

 is pointed out by experience. We do not consider that this fact is 

 difficult of explanation. Lime cannot alter the mechanical texture 

 of soils, nor give to the whole mass, the property of absorbing gases, 

 except by entering into chemical combination with their other con- 

 stituents. Such changes of character are not only the universal 

 consequence of chemical action, but the strongest proofs of its hav- 

 ing taken place. The case before us, is therefore, no more than one 

 of a large class in chemistry, where it is necessary to apply a chem- 

 .ical agent much diluted at first, while, after the action has once com- 

 ' menced, the strength of the agent may be gradually increased with 

 advantage ; and in the same way, upon poor and exhausted soils, a 

 large dose of calcareous matter may produce no benefit, or even 

 positive injury, while a lighter dressing may produce immediate good 

 effects, and prepare the soil to receive with advantage, larger quan- 

 tities. The addition of putrescent manures, enables the lands to re- 

 ceive a larger dose of lime even from the first, and the successive 

 dressings may in like manner be increased if green crops are plough- 

 ed in, or stable manure added. This is also consistent with theory, 

 for the surplus lime may be advantageously employed in absorbing 

 the gases generated by the decomposition. Still these are facts that, 

 although we may explain them in conformity with chemical princi- 

 ples, could not readily have been predicted before hand. 



One curious fact was observed by Mr. Ruffin, in his chemical 

 analysis of the soils of Virginia, namely, that even in regions where 

 the rock, by whose decomposition the soil was formed, was limestone, 

 not only did no carbonate of lime manifest itself by effervescence 

 with acids, but no precipitate was formed by the tests of lime in the 

 acid solution. He could not admit that in such soils, lime was ab- 

 solutely wanting, and therefore inferred, that it was in such a state 

 of combination, as to be neither soluble in water, or decomposable 

 by nitric acid. Such a combination is the oxalate of lime, but as he 

 has made no direct inquiry into its presence, and some of his cor- 

 respondents have questioned the probability of such an union exist- 

 ing, he has with the true spirit of an inductive enquirer, modified his 

 assertion until farther proof be obtained. We however, do not think 

 that so much modesty was necessary, for it can be shown that the 

 formation of oxalic acid, and its consequent combination by superior 

 affinity with lime, whatever may be its previous state of combination, 

 are at least probable, if not certain. 



