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Greensand from Marl of James SmWi's pits, Mannington Hill, 



near Salem. 



Description. — Colour of the granules, a rich dark olive-green; 

 size, rather large; forms 88-8 per cent, of the nnarl. 



Composition. — In 100 parts: 



Silica, .... 50-00 

 Alumina, - - - 6-99 



Protoxide of iron, - - 20-99 

 Potash, - - - 10-99 



Water, - - - 10-00 



98-97 



Comparing the details of these several analyses, we perceive 

 that the greensand even when of the greatest purity is not 

 absolutely constant, either in the nature of the ingredients which 

 enter into its composition, or in their relative proportions. The 

 per-centage of the silica is seen to vary from 47-5 to 51-5 ; that of 

 the alumina from 6 to 9-35 ; that of the protoxide of iron from 

 20-86 to 24-74; that of the potash from 9-96 to 12-96; and that 

 of the water from 5-5 to 9-5. We find, moreover, that, in some 

 instances, besides these elements, lime enters into the constitution 

 of the greensand, in other cases magnesia ; while occasionally 

 both occur. The amount of these earths is, however, always 

 inconsiderable. 



From the above series of analyses it appears that the mean 

 proportion of the silica is approximately 49-5 per cent.; that of 

 the alumina 7-3 ; of the protoxide of iron 228 ; of the potash 1 1-5; 

 and of the ivater 7*9 per cent.; while the lime when present 

 seldom exceeds one half per cent., and the magnesia is rarely 

 more than a mere trace. 



A comparison of the greensand of New Jersey with that of 

 Europe shows no essential difference in their chemical nature. 

 M Berthier, an able French chemist, has analyzed that of the 

 vicinity of Havre, in France, and reports the following as its 

 composition. 



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