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 way allied. 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 not a 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 land,* 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.f carbon, while the same ex- 

 tent of arable land yields in beet roots, without leaves, 936 lbs., or in 

 corn 1020 lbs. — from which it appears that equal surfaces of culti- 

 vated land, of average fertility, produce equal quantities of carbon. 

 Now supposing this carbon to be supplied from humic acid, dissolved 

 in the form of humate of lime, (the most soluble of its salts,) and con- 

 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 

 wood on the above named surface of land sufficient to account for the 

 absorption of humic acid supposed to take place, would be 91 lbs. 

 only, while it is proved that the same superficies actually produces 

 annually 2650 lbs. of fir wood. Whence, then, do plants obtain their 

 carbon 1 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 lbs. Hessian, equal in the form of carbonic acid to -x-io-Q of the 

 volume of the atmosphere. The value of humus in the soil (and it 

 must be remembered that as humus is entirely due to organic life, no 

 humus could have existed previous to the existence of vegetables) con- 



* One Hessian acre, equal to 26,917 English square feet. 



t One pound Hessian is equal to about eleven tenths English, and consequently 

 1000 lbs. equal 1102 lbs. English. 



