193 



is generally white or semitransparent quartz, existing usually in 

 relatively small amount, the clayey matter being ordinarily the 

 most abundant. This latter is of several tints, but is commonly 

 of a light gray or lead-colour. It is also occasionally chocolate- 

 coloured, brown, and even nearly white. Coating frequently the 

 surfaces of the green grains, it conceals their true colour, im- 

 parting its own hue to the entire mass. As it is somewhat adhe- 

 sive when moist, it gives to the stratum where it is abundant the 

 character of a partially plastic clay. Besides the white sand and 

 this clayey material, we often find a minute quantity of finely 

 divided mica mingled with the greensand. 



Subjecting the marl in the compound condition in which it 

 occurs in the stratum to analysis, mechanically performed, I have 

 ascertained the relative proportions of its several ingredients for 

 a great number of localities. A large body of results will be 

 presented in the section treating of the economical details of the 

 greensand formation. But in the mean time, with a view to 

 exhibit the prevailing composition of the stratum, the seven fol- 

 lowing analyses are presented. 



Analyses of the "Marl." 



A specimen from the pit of William Little, near Middletown Point, 

 Monmouth county. 



The material at this locality is of a light stone-gray, inclined to 

 greenish. Closely examined, the green granules are easily dis- 

 tinguishable. At a little distance it has the aspect of a light- 

 coloured clay. The greensand procured from it by washing is 

 of a light green colour. 



When separated into its constituents, 100 parts, afford : 

 Greensand, - 46-73 



Clay, - - 53-27 



Quartzose sand, - none. 



10000 



A specimen from Thorp's pits, near Squankum, Monmouth county, 

 {upper part of the bed.) 



This marl is of a dark leaden-gray colour, owing to the pre- 



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