02 now CROPS FEED. 



The mode or its Arisxin at once fu'^<j;ests its presence in the atmos- 

 phere. Saussure observed that common air contains some gaseous com- 

 pound or compounds of carbon, besides carbonic acid; and Boussin- 

 giiult lonnd in 1834 that the air at Paris contained a very small quantity 

 (from two to eight-milliontbs) of liydro^^en in some form of combina- 

 tion besides water. These facti agree witli the supposition that marsh 

 gas is a normal though minute and variable in-redient of tii(; atmosphere. 



Relation!!! oi" 3Ia,i-!^li CSas to Tegelsilioii.— Whether 

 this gas is absorbed and assimilated by plants is a point on wliich we 

 have at present no information. It might serve as a source both of car- 

 bon and hydrogen ; but as these bodies are amply furnished by carbonic 

 acid and water, and as it is by no means improbable that marsh gas it- 

 self is actually converted into these substances by ozone, the question 

 of its assimilation is one of little importance, and remains to be inves- 

 tigated. 



Schultz (Johnston's Lectures on Ag. C/iem., 2d Ed., 147) found on sev- 

 eral occasions that the gas evolved from jdants when exposed to the sun- 

 light, instead of being pure oxygen, contained a combustible admixture, 

 BO that it exploded violently on contact Avith a lighted taper. 



This observation shows either that the healthy plants evolved a large 

 amount ot marsh gas, which forms with oxygen an explosive mixture 

 (the fire-damp of coal-mines), or, as is most probable, that the vegetable 

 matter entered into decomposition from too long continuance of the 

 experiment. 



Boussingault has, however, recently found a minute proportion of 

 marsh gas in the air exhaled from the leaves of plants that are exposed 

 to sunlight whe7i submerged in water. It does not appear when the leaves 

 are surrounded by air, as the latest experiments of Boussingault, Cloez, 

 and Corenwinder, agree in demonstrating. 



Carbonic Oxide, CO, is a gas destitute of color and odor. It 

 burns in contact with aii', with a flame that has a fine blue color. The 

 result of its combustion is cnrbonic acid, CO + O = COj. 



This gas is extremely poisonous to animals. Air containing a few 

 per cent of it is unfit for respiration, and produces headache, insensi- 

 bility, and death. 



Carbonic oxide may be obtained artificially by a variety of processes. 

 If carbonic acid gas be made to stream slowly through a tube containing 

 ignited charcoal, it is converted into carbonic oxide, CO2 -t- C = 3 CO. 



Carbonic oxide is largely produced in all ordinary fires. The air which 

 draws through agrafe heaped with well-ignited coals, as it enters the 

 bottom of the mass of fuel, loses a large portion of its oxygen, which 

 there unites w ith carbon, forming carbonic acid. This gas is carried up 

 into the heated coal, and there, where carbon is in excess, it takes up an- 

 other proportion of this element, being converted into carbonic oxide. 

 At the summit of the fire, where oxygen is abundant, the carbonic oxide 

 burns again with its peculiar blue color, to carbonic acid, provided the 

 beat be intense enough to inflame the gas, as is the case when the mas» 



