SULPHUR IN ORGANIC NATURE. 299 



compound retains a small quantity of ammonia. This subject 

 bears with momentous importance on the production of arti- 

 ficial manures. Besides being of volcanic origin, ammonia 

 exists in nature in the salts having ammonia for their base. 

 These of course should be mentioned as a source of nitrogen 

 in mineral nature, to which the natural nitrates are to be 

 added. Nitrogen exists also in the compound mineral in- 

 flammables, which, however, have a vegetable origin, common 

 pit-coal being a principal example. Mtrogen does not exist 

 as a common element of the rocks of the crust of the earth. 



Ultimate Elements in Organic Nature of the Second Order. 



Chlorine. Chlorine is known in organic nature merely as 

 combined with sodium, forming sea-salt. In this form it is 

 very essential. In mineral nature it exists only in the form 

 of chlorides. 



Sulphur. Sulphur abounds in mineral nature, particularly 

 in combination with metallic bodies and in volcanic forma- 

 tions. It appears to be an essential constituent of many 

 organic bodies ; and in particular, it exists, though in minute 

 proportion, in the principles termed the proteine compounds, 

 which constitute the chief forms of azotised animal aliment. 

 Its presence in the soil, then, where crops are reared for food, 

 must be of the last importance, a point not to be neglected in 

 the contrivance of artificial manures. It has long been re- 

 marked that the presence of sulphur is always distinguishable 

 in the order of cruciferous plants to which the turnip and the 

 coleworts belong. Minute as is the proportion of sulphur in 

 those organic bodies in which it has been observed to exist, 

 there can be no doubt that any deficiency even of that small 

 proportion must necessarily be attended with a failure of 



