477 



nourishment to plants. A third reason, and certainly a strong fact in 

 the case, is, that the humus in a forest, so far from being diminished by 

 the growth of wood, is continually increasing. It is so likewise in a 

 cultivated field, where the produce of the field is returned in the form 

 of manure. 



Berzelius is reported to have altered his opinions of the nature of 

 geine by a more exact analysis of its composition, and now denies its ex- 

 istence as a proximate principle ; and Dr. C. T. Jackson, who has dis- 

 tinguished himself as a chemist by his analytical researches, appears to 

 have made, without knowing what had been done by Berzelius, the 

 same discoveries, in ascertaining that the substance called geine is only 

 a combination of crenic and apocrenic acids, with some other substanc- 

 es, all of which are not yet determined. How many of these may 

 have been, as suggested by Dr. Dana, the mere product of chemical 

 manipulation, or whether any of them, are questions which, in the pres- 

 ent state of the inquiry, cannot be determined. Upon the supposition 

 that these are original and fixed elements in the composition of geine, 

 we consider Dr. Jackson entitled to much honor for his investigations. 

 All truth is valuable ; but in the present condition of our knowledge, 

 in a practical view, these points are not of great importance, or rather 

 not of immediate utility. According to the principles of Liebio-, Ras- 

 pail, Dana, Jackson, Hitchcock, and others, the presence of humus in a 

 soil is, quoad hoc, an indication of fertility. Now, whether it be a prox- 

 imate element, or a mere combination of crenic and apocrenic acids 

 with other substances, though exceedingly interesting to the philosophic- 

 al inquirer, is, without some further light on the subject, of little mo- 

 ment to the farmer. Dr. Jackson has not, as we understand, discovered 

 either of these acids in the plants themselves ; he has not as yet shown 

 us how they are to be used, or what part they perform in vegetation. — 

 He is not able, by any artificial process which he can adopt, separate 

 from the vegetable organism, to produce an atom of geine ; and how- 

 ever nearly he may have approached it, and we commend him for ev- 

 ery step in his progress, he has by no means reached the ultima thule ; 

 for crenic, and apocrenic, and ulmic acids, are themselves resolvable 

 into certain proportions of carbon, hydrogen, nitrogen and oxygen. 

 The question, however, whether geine constitutes in itself the food of 

 plants in its solution by water or by some alkaline substance, or whether 

 it merely acts as an instrument of the supply of carbonic acid to the 

 plant in the first stages of its progress, is another question which is cer- 

 tainly not without its difficulties. 



