6 OF THE ASSIMILATION OF CARBON. 



analysis of Stein, 64 per cent. All these analyses 

 have been repeated with care and accuracy, and the 

 proportion of carbon in the respective cases has been 

 found to agree with the estimates of the different 

 chemists above mentioned ; so that there is no rea- 

 son to ascribe the difference in this respect between 

 the varieties of humus to the mere difference in the 

 methods of analysis or degrees of expertness of the 

 operators. Malaguti states, moreover, that humic 

 acid contains an equal number of equivalents of 

 oxygen and hydrogen, that is to say, that these ele- 

 ments exist in it in the proportions for forming 

 water ; while, according to Sprengel, the oxygen is 

 in excess, and Peligot even estimates the quantity 

 of oxygen at 1 4 equivalents, and the hydrogen at 

 only 6 equivalents, making the deficiency of hydro- 

 gen as great as 8 equivalents. 



It is quite evident, therefore, that chemists have 

 been in the habit of designating all products of the 

 decomposition of organic bodies which had a brown 

 or brownish-black colour by the names of humic 

 acid or humin, according as they were soluble or 

 insoluble in alkalies; although in their composi- 

 tion and mode of origin, the substances thus con- 

 founded might be in no way allied. 



Not the slightest ground exists for the belief that 

 one or other of these artificial products of the de- 

 composition of vegetable matters exists in nature 

 in the form and endowed with the properties of the 

 vegetable constituents of mould ; there is not the 



