SULPHURETTED HYDROGEN 39 



in 'moist places or in stagnant pools, and may 

 often be seen rising in bubbles in marshy places. 

 In warm weather, and when vegetation com- 

 mences to decay in the fall of the year, the 

 amount formed is largely increased. It is called 

 marsh gas, and its presence is the direct cause 

 of the malaria of chills and fevers or the ague. 

 It is largely generated in the distillation of soft 

 or bituminous coal, and when mixed with atmos- 

 pheric air, is the much dreaded fire damp, the 

 explosion of which is so fatal to miners. 



This gas is also given off with carbonic acid 

 during the fermentation of compost heaps, or 

 any large deposits of vegetable matter. It is 

 present in all soils containing much decaying 

 vegetable matter, and is a source of carbon and 

 hydrogen to the growing plant ; but to effect this 

 a decomposition of its elements must be effected. 



When it is present in large quantities, it is 

 probable that it is just as poisonous to vegetable 

 as it is to animal life, and shows insufficient 

 oxidation of the carbon. 



SULPHURETTED HYDROGEN. 



Sulphuretted Hydrogen is a gaseous com- 

 pound of sulphur and hydrogen, and may be 

 readily detected by the similiarity of its odor to 

 rotten eggs. Water absorbs about three times 



