229 



" It contained almost nothing soluble in water, gave no 

 indication of nitrate or of ammonia, and only very faint 

 indications of any nitrogenized or animal matters. 



" The soil consists of trap-rock in process of disintegra- 

 tion, and the two columns of soluble and insoluble in acid 

 shew the process of the decomposition of the rock. The 

 very finest particles of clay obtained by elutriations, when 

 digested with acid, leave a residue of dark-brown parti- 

 cles, differing from the coarser in being more mixed with 

 and incmsted over by the silica separated from the 

 dissolved basis. The largest particles, when washed clean 

 and examined by a magnifier, shew the appearance of the 

 original rock. The black color is due to the original 

 rock. The color is somewhat browner than that of the 

 sample of trap-rock sent with it, owing, no doubt, to the 

 oxidation of some of the black oxide to red oxide. The 

 appearance of extreme blackness in the soil, when it looks 

 blacker than the rock, is fallacious, and is principally due 

 to the presence of water. When powdered and dried, the 

 soil looks browner than the rock, not blacker. 



" I have omitted in my analysis of No. II. to notice the 

 presence of chlorine, as the quantity was so minute that 

 it could not be estimated. No doubt it exists as a trace 

 of chloride of sodium, or common salt, which is found 

 in almost all natural waters." 



