Economical Geology of Massachusetts. 365 



condition of the organic matter which constitutes the nourish- 

 ment of plants.' 



The time at his command, however, was inadequate to a rigid 

 analysis of these soils, according to the rules laid down for the 

 nicest processes of quantitative research. Being forced to con- 

 duct many analyses contemporaneously, the use of silver and 

 platinum vessels was of necessity out of the question ; nor was 

 there room to verify results by repetition ; still he believes that a 

 sufficient approximation to the truth was secured, to answer the 

 purposes intended. 



The almost total absence of carbonate of lime is a remarkable 

 feature in the soils of Massachusetts. But seven specimens of 

 the whole number effervesced with hydrochloric acid, when ex- 

 amined with the utmost care to observe this phenomenon ; nor 

 did either of these examples afford carbonate of lime in a higher 

 ratio than about 3 per cent. 



It was a leading object in the research to determine the quan- 

 tity of finely divided matter in the soil, since the best soils are 

 usually characterized by their fineness. Prof H. thinks the 

 main defect of their soils to consist in the coarseness of their tex- 

 ture, and this he very properly attributes to the circumstance of 

 their originating, for the most part, directly from primary rocks. 



The salts soluble in water, equalled from 1 to 2 parts in a 

 thousand of the soil, and in every case it was believed to contain 

 sulphate of lime (gypsum.) Carbonate of magnesia was also 

 very frequently an ingredient, though in mere traces. The pres- 

 ence of soda and potassa was not determined. The peroxide of 

 iron exists from 1 to 4 per cent., and upwards in few instances. 

 Prof H. regards this last as an useful ingredient in soils. The ra- 

 tio of the alumina to the other ingredients varies from 1 to 18 

 per cent. The instances are common in which he found it above 

 10 per cent., which is beyond what might have been supposed 

 for a region where the argillaceous formations are so uncommon 

 as they are in Massachusetts. 



In respect to the earthy ingredients of a soil, it is undoubtedly 

 true that a very wide diversity of constitution is compatible with 

 fertility, provided the mechanical condition, and the proportions 

 of salts and organic matter are propitious. Prof H. is of opinion 

 ttiat ' the salts especially admit of but little variation without 

 producing sterility, either by their deficiency or excess ; and 



