rae 
.*% 
Bibliography. * 179 
of muriatic acid, according to the analysis of Stein, 64 per cent. It 
is quite evident, therefore, that chemists have been in the habit of de- 
signating all products of the decomposition of organic bodies, which 
had a brown or brownish black color, by the names of humic acid or 
humin, according as they were soluble or insoluble in alkalies; al- 
though in their composition and mode of origin, the substances thus 
confounded might be in no wayvallied. Not the slightest ground ex- 
ists for the belief that one or other of these artificial products of the 
decomposition of vegetable matter exists in nature, endowed with the 
properties of the vegetable constituents of mould; there is nota shad- 
ow of proof that one of them exerts any influence on the growth of 
plants, either in the way of nourishment or otherwise.’ 
This position is maintained at length, by a series of close arguments 
and calculations, made with the object of ascertaining the quantity of 
carbon contained in a given quantity of fir, pine and birch wood, of 
grain, of beet roots, and of hay, growing upon forty thousand square 
feet (Hessian) of Jand,* either forest, arable, or meadow, according to 
the produce. These estimates are made with great care, from the 
best analyses, and show that forty thousand square feet of wood and 
meadow land produce annually 1007 Ibs.t carbon, while the same ex- 
tent of arable land yields in beet roots, without leaves, 936 Ibs., or in 
corn 1020 Ibs.—from which it appears that equal surfaces of culti- 
veyed into the plants by means of rain water; under the most fa- 
Vorable circumstances which can be supposed to exist, even allowing 
that potash, soda, and the oxides of iron and manganese, have the 
same capacity of saturation as lime, by humic acid, the quantity of 
vo ‘the above named surface of land sufficient to account for the 
absorption of humic acid supposed to take place, would be 91 Ibs. 
only, while it is proved that the same superficies actually produces 
annually 2650 Ibs. of fir wood. Whence, then, do plants obtain their 
carbon? Undoubtedly from the atmosphere, by decomposing the 
carbonic acid which is its constant constituent. Prof. Liebig shows 
that the aggregate weight of carbon in the atmosphere exceeds 3000 
billion Ibs. Hessian, equal in the form of carbonic acid to y755 of the 
Volume of the atmosphere. The value of humus in the soil (and it 
‘ust be remembered that as humus is entirely due to organic life, no 
h 
umus could have existed previous to the existence of vegetables) con- 
Wiis dimmers 
* One Hessian acre, equal to 26,917 English square feet. 
1 t One pound Hessian is equal to about eleven tenths English, and consequently 
000 Ibs, equal 1102 Ibs. English. 
