476 



" Geology of Massachusetts," on geine or humus, and some views of 

 Dr. C. T. Jackson, of Boston, on the same subject. 



The views of these gentlemen in some measure conflict with each 

 other, and with those of Liebig. I shall not presume to arbiti'ate be- 

 tween them, but only to remark on them, in a very few words, with a 

 perfect respect for all the parties concerned. The eminent Swedish 

 chemist, Berzelius, had discovered in several vegetable substances, a 

 residuum, which he regarded as the proper food or pabulum of vege- 

 tables, and which he denominated humus or geine. Dr. Dana, by his 

 independent researches, had arrived at the same result. This geine or 

 apotheme was found to be the universal result of decayed vegetation ; 

 and soils are in general found productive or otherwise, as this vegeta- 

 ble substance or residuum is more or less abundant in them. The 

 opinion of Dr. Dana has been that geine in a dissolved state is taken up 

 as the food of plants. If obliged to relinquish this ground, and with 

 Liebig, regard geine as only a source of carbonic acid to plants, he 

 would regard its value to vegetation in the same light. But he obviates 

 in a most ingenious manner one of the difficulties of Liebig, in respect 

 to the solubility, or, we may more properly say, the solution of geine, 

 by showing that it contains whhin itself the instrument, to a considera- 

 ble degree, of its own resolution, in the water forroed by the union of 

 the hydrogen of the geine with the oxygen of the atmosphere. " The 

 amount of water produced in this case," he remarks, " is truly aston- 

 ishing. It has been found equal per hour, from an acre of fresh 

 ploughed sward, to 950 lbs. This is equal to the evaporation per hour 

 from an acre, after most copious rains. To show that this depends 

 upon the decomposition of the geine, the quantity of water evaporated 

 per hour in the day-time, from a well-manured acre, was found equal 

 to 5000 lbs." 



That humus or geine does not constitute the actual food of plants, 

 would seem to be established by vai'ious considerations. Liebig has 

 shown by several calculations, as exact as the nature of the case would 

 seem to admit of, that the amount of humic acid contained in any soil 

 is insufficient to supply the carbon in the average product of that soil, 

 in the proportion of 91 to 2,(550. Secondly, volcanic soils containing 

 not the slightest trace of vegetable matter, as is evident from their ori- 

 gin, with a due mixture of earths, are among the most fertile in the 

 world. The ashes being exposed to air and moisture, a soil is gradual- 

 ly formed, and the decomposed lavas furnish alkalies in abundance, 

 which, by being exposed to air and moisture, become the source of rich 



