SUBSTANCES YIELDING SULPHUR. 61 



materials which it may meet in its course. The substances 

 thus dissolved communicate to the water properties which are 

 not possessed by pure water. Water procured from springs or 

 wells is found to be very rarely deficient in soluble salts of sul- 

 phuric acid. The liquid obtained by lixiviating good soil from 

 garden or arable land also contains very appreciable quantities 

 of these salts. 



The facts now detailed leave little doubt as to the source 

 whence plants obtain their sulphur. As far as our knowledge 

 extends, they receive their sulphur from the sulphates dissolved 

 in the water absorbed by their roots from the soil. 



Ammoniacal salts, particularly sulphate of ammonia, are 

 rarely detected in spring water ; but this is owing to the con- 

 stant presence of supercarbonate of lime, which effects their 

 decomposition, and allows the escape of ammonia during the 

 evaporation of the liquid for the purposes of analysis. 



According to our view, sulphate of ammonia is of all com- 

 pounds containing sulphur the one most fitted for the assimilation 

 of that element. Sulphate of ammonia contains two elements, 

 both of which are equally necessary for the support of vegetable 

 life ; these are sulphur and nitrogen, and they form constituents 

 also of vegetable albumen, fibrin, and casein. But what is still 

 more worthy of observation, sulphate of ammonia, viewing it 

 according to the proportion of its elements, or what is termed its 

 empirical formula (SO ,, N H 3 ,), may be considered as a com- 

 pound of water with equal equivalents of sulphur and nitrogen. 

 Thus, by the simple removal of the elements of water from this 

 compound, its sulphur and nitrogen might be enabled to pass over 

 into the composition of the plants. 



The ingredients of plants containing sulphur are so composed 

 that one equivalent of sulphur exists for every 25 equivalents 

 of nitrogen. Hence it is obvious that much more ammonia 

 must be offered to plants than that contained in the form of sul- 

 phate of ammonia, if all the sulphur of the latter is to become a 

 constituent-of the organic ingredients alluded to. 



This bears a complete analogy to the assimilation of the car- 

 bon and nitrogen furnished to plants in the form of carbonate of 

 ammonia. This salt may contain two equivalents of carbon to 



