COMPOSITION OF MARSH SOIL. 245 



amount of phosphoric acid found, as above stated, is the result 

 of their united influence. 



The combination of phosphoric acid with the oxide of iron, 

 the form iu which I observed it, is due to a secondary reaction : 

 namely, that of soluble iron compounds on soluble phosphates. 

 This process is highly favored by the reducing action of the 

 decaying vegetable matter on the sesquioxide of iron within 

 the soil, as well as by the continual production of carbonic 

 acid from the same source. 



The latter renders the phosphate of protoxide of iron sol- 

 uble, and thereby promotes its successful diff'usion through- 

 out that body of the soil which is permeated by the soil 

 water. As the conditions for the solution of insoluble 

 phosphates, as phosphate of lime, are favored in an unusual 

 degree by the presence of salt, it becomes a matter of economy 

 to check the reaction of the saline water on the natural 

 resources of the soil as long as the excess of decaying vege- 

 table matter can furnish carbonic acid enough to render an 

 eflicient amount of that plant-food available. 



To leave the marsh lands, therefore, for any length of 

 time under the unrestricted influence of both agencies for the 

 distribution of the ready plant-food, is, from an agricultural 

 stand-point, to say the least, a bad economy. The loss of their 

 natural soil resources will increase in magnitude in the same 

 desfree as the present accumulated vegetable matter will be 

 permitted to waste away without securing its soluble essential 

 plant constituents by getting control of the drainage. 



The close relation which evidently exists between the soil 

 in the marshes and the beach-sand on their eastern outskirts, 

 rendered it very desirable that some more definite information 

 reofcirdinor its chemical character should be secured. 



My analytical inquiries are not far enough advanced to pre- 

 sent here exact quantitative results, yet they are already suffi- 

 ciently decisive to assert that the sand — being apparently iu 

 its main bulk of granitic origin, consisting, therefore, of a 

 series of valuable mineral species, and not merely of fragments 

 of quartz — must be regarded, on account of its chemical 

 qualities, as far as it has entered by natural causes the soil of 

 the marshes, as a very valuable constituent ; and for the same 



