342 N. H. STATE AGRICULTURAL SOCIETY. 



lime or oxide of iron, is present, the sulphuric acid may 

 he neutralized, but in such a chemical activity plants would 

 fare badly. 



A visit to the Copperas Works, at Strafford, Vermont, is 

 very instructive, as showing how unfavorable to plants, is 

 the decomposition of the iron pyrites, which by thousands 

 of tons is converted into sulphate of iron or copperas. 



So the sulphuret of calcium of the gas works, on exposure 

 in the fields, must be oxidized and the sulphur become sul- 

 phuric acid, and the calcium become lime, and the two, if 

 united, gypsum. But in this play of affinities the actian 

 on plants would in all probability be injurious. 



The gas lime is undoubtedly a mixture of lime, carbonate 

 of lime, sulphuret of calcium and sulphuret of hydrogen — 

 presenting the elements of a vigorous chemical reaction. 



In this case, and in all similar ones, experiments should 

 be made under circumstances, involving little cost and risk 

 of damage, and the results cannot fail of giving a rule of 

 practice. Yours truly, 



6. r. H. 



Dr. Dana, whoso reputation as a chemist is well known, 

 writes us the following : — 



" Gas lime contains sulphuretted hydrogen, sulphuric acid 

 and ammonia. It cannot be used agriculturally till it has 

 been exposed to ilie air for some months, say a year, by 

 which it is converted into sulphate of Jime and ammonia, 

 and car])onate of lime. In this state, mixed with three 

 times its bulk of soil, it forms a useful top dressing — or it 

 may be added, before mixing with soil, to the compost heap 

 or to meadow muck, say two bushels to the cord." 



