40 AMERICAN MANURES. 



its volume of this gas, and some sulphur springs 

 contain large quantities of it. It is colorless, 

 inflammable, and when breathed, highly poison- 

 ous. Being considerably heavier than common 

 air, it may be poured into cavities and holes, and * 

 has been successfully used in killing vermin and 

 rats. The gas is produced in marshy stagnant 

 places, and in fish ponds, where vegetable matter 

 is undergoing decay in the presence of the 

 sulphates of the metals -in solution, as the 

 sulphate of iron, gypsum or land plaster; and in 

 old pasture lands it may be frequently detected, 

 even by the sense of smell, around the roots of 

 the sod. As in the egg, so in other decaying 

 animal matter, especially when the air is in a 

 manner excluded, this gas is formed. The 

 presence of this gas is detrimental to vegetable 

 life ; where it exists in considerable quantity it 

 prevents the free excess of oxygen, without 

 which plants as well as animals cannot live. 

 Plants have not the power of rejecting poisonous 

 substances any more than animals. The presence 

 of these gases in the soil is a proof that it is un- 

 fitted for the proper and luxuriant growth of 

 plants, and that an imperfect oxidation of the 

 soil exists, that cannot too soon be remedied by 

 cultivation and the addition of active manurial 

 substances. 



