ATTRACTION OF WATKll BV AIR. 24,5 



ike hygrometrical attradion to diminifti with the abforptlon of 

 water, and to inereafe with the lofs of the fame; confequently 

 an union produced by this force, may be dilTolved by the pre- 

 fence ot a body, which contains lefs water, and therefore at- 

 tra<51s it more powerfully. 



Atmofpherical air may be concluded to pofTefs the power Atmofpherlcal 

 defcribed above, from the chanpres and effefis, which are ob- ?"P''5^fl*« this 

 r LI- ir-u- -/^ -r^ r^ /- •• attrattioH, 



lervable in tlie toliowing inltances: Firft, Atmolphencal air 



takes the water ot cryftaUization from various falls; it there- 

 fore overcomes the affinity, which unites the component parts 

 of thefe cryltals, Secondly, The fame hygrometer denotes a 

 greater degree of humidity at one time, than at another, 

 though the height of the thermometer be the fame; confe- 

 quently the hygrometrical attradion of the atmofphere is vari- 

 able under equal degrees of temperature; becaufe this force 

 is evidently conffant in an inftrument kept in an uniform heat* 

 Third, If two vefiels be expofed, at the fame time to the air, 

 one of which contains dry potafti, and the other a dilute folu- 

 tion of the fame; the former will acquire weight, while the 

 other grows lighter. The laft fad (hows, that atmofpherical 

 air may be faturated with moifture, in refped of one body, ■ -^ 



and be at the fame time in a very different lituation relative to 

 another; fo that evaporation evidently arifes from an excefs of 

 hygrometrical attraction in the atmofphere; on the contrary^ 

 the produ6iion of dew depends upon a fimilar excefs in the 

 bodies on which it is formed. 



I may be a(ked, after making this open declaration of my Atmofpherical 

 fentiments, which of" the conflituent gafes of the atmofphere ^"^ ^ ^""P'^ gas, 

 combine with water? The proper reply to the queftion appears 

 to be this: It is atmofpherical air; which I confider to be a 

 homogeneous gas, for the following reafons: — Firft, The at- becaufe It is 

 mofphere is diaphanous; which could hardly be the cafe, were <i'aphanous^ 

 it a mat's of uncombined fluids of different fpecific gravities; 

 for, had fuch an arrangement been formed, the rays of the 

 fun would have fuffered a multiplicity of refradions, in their 

 approach to the earth ; and total darknefs, or at beft a dim 

 twilight, would have been the confequence, had our planet 

 been fhrouded by a covering of heterogeneous gafes. Thus 

 the atmofphere appears to be homogeneous, from the confi- 

 deration of its tranfparency. — Secondly, A given meafure of becaufe fmart 

 m'lgen is heavier than an equal bulk of azote, under fimilar 3le to SL 



circumftances j 



