OUJ EVAPORAfipN, 



3. In the triangle M A H, the angle jjt M is equal to the 

 difference of the known angles' G M A, Q M H ; and th« 

 angle at H, together with the two j5des A M^ H M are alio 

 known. Whence the third fide H A or diftancc; frtjn) i\\e houfe 

 to the obje6l A may be found. 



6. Ladly the bearing of any of the three fides gf the tfir 

 Jungle MAG may be had from the known difference of J^ti- 

 tude and meridianal diftance of its extremities : And thi? bear? 

 mg may with eafe be then applied to Qiew the bearings pf t|)e 

 linesIIA,HM, HG, 



W. N. 



II. 



Experimental' Ejpiys on the Confiitiition of mixed Gafes; on th^, 

 Force of Steam or Vapour from Water and other Liquids in 

 different Temperatures, both in a Torricellian Vaciaun and in 

 Air; on Evaporation; and on the Expanfion of Gafes by Heat, 

 ^JohnDalton. 



(Concluded from Page 273, Vol, VI. j 

 ESSAY III. 



ON EVAPORATION. 



VV HEN a liquid is expofed to the air it Is gradually dlffi- Evaporation 



pated in it. The procefs by which this effect is produced we ^^^"c<** 



call evaporation. 



Many philofophers concur in the theory of chemical folution : Theory which 



atmofpheric air, it is faid, has an affinity for water: it is a ^^"'^^^ ^"f P°" 

 n • 1 • 1 t • r I UT X X • J T T^^^^'^n to chemi- 



menitruum in which water is loluble to a certain degree. It cal folutiop ia 



is allowed notwithftanding by all, that each liquid is convert- ^if"~ 

 ible into an elafjic vapour in vacuo, which can fubfift inde- 

 pendently in any temperature; but as the utmofl forces of thefe 

 vapours are inferior to the preffure of the atmofphere in ordi-r 

 nary temperatures, th,ey are fuppofed to be incapable of exift- 

 Ing in it in the fame way as they do in a torricellian vacuum; 

 hence the notion of affinity is induced. According to this the- 

 ory of evaporation, atmofpheric air (and every other fpecies 

 qf air for aught that appears) diffolves water, alkohol, ether, 

 acids, and even metals. Water below 212° is chemically 

 combined with the gafes; above 212® it affumes a new form. 



