364 TRANSACTIONS OF THE 



staiF of life." Not to meBtion many others, the peach contains coinpounda 

 of lime, as does the locust tree. Now neither of these three plants will 

 flourish in a soil that contains no lime. The first will run to straw, and 

 have empty ears ; the second will be unhealthy ; the third will be liable 

 to the attack of insects, and will not acquire any useful dimensions. 



5. The next reason for the use of lime is to be found in its power to 

 neutralize acids. Practical men long spoke of sour soils before scientific 

 men were willing to admit of their existence. These soils are marked by 

 the growth of useless or noxious plants, the most characteristic of which is 

 sheep sorrel. The presence of this plant manifests the existence of oxalic 

 acid in the soil, and for this acid lime in any or every state of combination, 

 is a remedy. Under the same head may be classed the use of lime in soils 

 which contain sulphate of iron. This is the case with many of the fields 

 overlying gneiss and mica slate rocks in Westchester count}^ and on our 

 own island. This salt of iron is decomposed by lime and its carbonate, 

 forming the valuable compound sulphate of lime. 



0. The carbonate of lime, in a state of fine powder, has a strong mechan- 

 ical attraction for the gases which are yielded by decomposing vegetable 

 and animal substances. When soils contain this earthy constituent, these 

 gases remain, to be taken up as they are needed by plants ; but where the 

 soil is sandy, and no carbonate of lime is present, these gases are rapidly 

 dissipated in the air. It may thus happen that the manure spread by one 

 farmer upon his sand, shall enrich the field of his neighbor who has charged 

 his soil with carbonate of lime, and maintains it in fine tilth. The value 

 of fallowing is due to the absorption of gases by the soil, and will be much 

 greater iu soils containing carbonate of lane, than in those which do not. 



He proceeded in the second place to consider the manner of applying 

 lime in agriculture. As an introduction to this branch of the subject, he 

 thouglit it expedient to state to his hearers not versed in science, a few 

 chemical facts. Lime is an earth, which, when free from combination, is 

 alkaline and highly caustic. It has necessarily a very high affinity for 

 acids, with which it combines to form compounds, which are styled neu- 

 tral, because they manifest the characters of neiiher of their compounds. 

 He thought it proper to refer to this familiar fact, because one of the gentle- 

 men who preceded him, had, in speaking of plaster, referred to the presence 

 of sul})huiic acid in it, in a way which might have left the impression that 

 aci.i properties were still manifest in that compound. 



The compounds of lime, connected with our subject, are, the carbonate, 

 the sulphate, and the phosphate. The two first occur in nature in combi- 

 nation with water, which forms a notable portion of their solid mass. Both 

 part with this M'atcr when heated, but the sulphate of lime is not decom- 

 posed, while the carl:onie acid is driven off from the carbonate by heat. 

 The sulphate of lime, after being deprived of its water and permitted to 

 cool, attracts that substance with great avidity, insomuch that if it be raised 

 with v.'ater to the consistence of a thick cream, the mixture speedil}^ be- 

 comes solid. Hence the use of sulphate of lime in the mechanic and fine 

 arts, and its familiar name of plaster. 



