206 



Greensand of Havre, in France. 



Composition. — In 100 parts: 



Silica, .... 50 



Alumina, .... 7 



Protoxide of iron, - - 21 



Potash, .... 10 



Water, - - - - 11 



Loss, .... 1 



100 



The late laniented chemist, Dr. Edward Turner of London, 

 also examined with great care the chemical constitution of the 

 greensand of Kent, in England. 



His experiments gave in the 100 parts: 



Silica, .... 48-5 

 Alumina, ... i7-o 



Protoxide of iron, - - 22-0 

 Potash, ... a trace. 



Magnesia, ... 3-8 



Water, .... 7-0 



98-3 



The absence of potash in the green granules of the English 

 greensand, and the large proportion of magnesia are facts not a 

 little remarkable. 



ECONOMICAL RELATIONS OF THE GREENSAND FORMATION. 



Abundant evidence might be adduced to prove that the true fer- 

 tilizing principle in marl is not lime but potash. The analyses which 

 have been made, give us in several cases no lime at all, and where 

 a small proportion of lime is present in the green granular mineral, 

 it is in a combined state, chemically united with the other ingre- 

 dients, and not traceable to the organic remains, which are in 

 many of these instances not present in the stratum. Besides, the 

 quantity of shelly matter, even where the shells are plentiful, is so 



