1836.] 



FARMERS' REGISTER. 



57 



and vein me. This has been proved by the expe- 

 riments of the elder M. de Saussure and of Davy. 

 The quantity of aqueous fluid contained in the air, 

 varie.s accordmo' to the teni|)erature of the atmos- 

 phere, and increases in proportion as tiiat is eleva- 

 ted. At 50° Fahrenheit, it forms in volume nearly 

 TjL of the atmospheric fluid; and as its densitv is 

 to that of the atmosphere in the proportion of 10 

 to 15, it constitutes nearly ,V °^' i^^ weight 

 (Davy.) 



The aqueous fluid forms, when the atmospher- 

 ic temperature is 34° Centiirrade = 93°.20, (Da- 

 vy says at 100°,) yV o^ the volume ol" the air, and 

 ttY of its weight. 



The elder M. de Sau.=;sure, in his beautiful 

 Treatise vpnn the Ui/grmmter, has determined the 

 weight of the water contained in a cubic foot of 

 air, at (hfierent temperatures, and has prepared 

 the lollowing table of the results. 



''Consequently," adds M. de yaussure, '•! do 

 not think we are far from the truth, in assigning 

 11 grains of water to saturate a cubic foot ot' air, 

 at the temperature of 15° of Reaumur," (equal 

 to 65°.75 Fahrenheit.) "The solution of these 

 11 grains of water in a cubic foot of air at the 

 teaipeniture of 15° Reaum. (equal to 65°. 75 F.) 

 increased the density ol" the air so much, that the 

 barometer, which b;>l!jre was at 27 inches, rose to 

 27 inches 5 lines 79,411, that is to say, about 27 

 inches 6 lines; consequently, the density of the 

 air, or its volume in tiie receiver, was increased 

 about --■,."' 



When the temperature of the air is dinnnished, 

 the acjueous fluid is conden.sed, and appears in the 

 atmosjjhere in the lorm of vapor, and is deposited 

 in the state of de.v. The moisture of the night 

 air from this cause, during the heat of summer, 

 restores vegetation from that state of languor pro- 

 duced by the too great war.mth of the day. 



Oxygen and azote have been classed among 

 the simple bodies; carbonic acid and aqueous flu- 

 id among the compound bodies, of which the 

 principal constituents are known, and which can 

 be formed and decomposed at will. 



100 parts of carbonic acid contain — ■ 



carbon 27.36 



oxygen 72.64 



10 parts of water contain, hj'drogen 11.08 



oxygen 88,94 



Oxygen and azote constitute, essentially, the 

 atmosphere; since, when the two other jsrinciples 

 are separated fi:om it, it still retains nearly all its 

 Vol. IV— 8 



characters of form, elasticity, &c. It however 

 loses its most important powers of influencing ve- 

 getation; so that all the substances found in the 

 atmosphere are necessary to the production and 

 renewal of the phenomena which the three king- 

 doms present to us. 



Of the four principles of which 1 have just spo- 

 ken, as constituting the atmosphere, the aqueoua 

 fluid is that which appears tlie least closely uni- 

 ted to the others; since a change of temperature 

 alone is sufficient to produce a change of its pro- 

 portions; whilst azote, oxygen, and carbonic acid 

 |)reserve, always, nearly the same relative propor- 

 tions; nor can they be varied, or disunited, by 

 means of compression or change of temperature. 

 The aqueous fluid does not rise to a great height 

 in the atmosphere; for, according to the reports of 

 those experimentalists who have arrived at their 

 conclusions by the assistance of air-balloons, the 

 higher regions of the atmosphere are very dry, so 

 as to produce, by the avidity with which they ab- 

 sorb the moisture fi'om the boat of the balloon, a 

 warping and cracking of its boards, as if they 

 had been exposed to a strong heat. This effect is 

 produced by the dryness of the atmosphere and 

 the diminution of its specific gravity. 



The manner in which the atmospheric elements 

 are united is woriiiy of notice. This union is suf- 

 ficiently strong to counterbalance the difference 

 in their specific gravities, and not to allow them 

 to be separated by compression, or the tumultuous 

 agitation of the air; and yet it permits the various 

 principles to be decompojicd and isolated, by pre- 

 senting to them bodies jbr which they have some 

 slight affinity. Thus, if v/e inclose under a bell- 

 giass any volume whatever of atmospheric air, 

 ihe aqueous fluid may be extracted from it, by the 

 calcined muriate of lime. The combustion of 

 phosphorus in it will absorb the oxygen gas; 

 lime-water, or the caustic alkalies, will combine 

 with the carbonic acid; and nothing will remain 

 but azote, which is tlie portion that has the least 

 tendency to form combinations. 



This weak state of union among the principles 

 contained in the atmosphere is necessary, in order 

 that they may exert their powerlul and constant 

 action upon all the various bodies which cover the 

 surliice of the globe; the composition and decom- 

 position of which cannot be eflected othexwise 

 than by the means of these agents. 



Independently ol those bodies which es.senfial- 

 ly cons;itute the atmosphere, there are mingled in 

 it the exhalations constantly arising from the 

 earth; these are again disengaged from the air, 

 and preciphated, as soon as the heat, or any other 

 cause which occasioned their ascension, ceases to 

 act upon them. These exhalations modify the 

 properties of the air, and aliect its purity. The 

 oxygen and the water of the atmosphere become 

 impi-egnated with the particles of the exhalations 

 which are deposited with them upon the sur- 

 faces of other bodies, where they remain in con- 

 tact, or enter into combination, with them. The 

 origin and dissemination of many maladies may 

 be traced to this source; the germ of them is 

 carried through the air by the aqueous fluid. And 

 for the same reason it is, that intermittent fevers 

 are endemic in those situations where large quan- 

 tities of animal or vegetable matter are undergo- 

 ing decomposition, as upon the borders of poods 

 and marshes; and that miasm, which arises from 



