PAPER BY PROF. BEZOLD. 285 



of eondeiit^atiou ami of dissolution, that is to say, between the ordinates 

 ^1* and y.,*, then will the resulting mean temperature i—^^* + *^* be 



attained quicker when we go from .f/i* towards ?/2* tliau when we go 

 from y-z' towards y^*. For siuce ^ > ^3 therefore for t = i i^ti*-\-ti*) the 



mixing ratio — ^ > 1, that is to sav, the mixture shows the avera^-e 



temperature, although so far as mass is concerned the colder component 

 is in excess. According to this, if we mix saturated cooler air with 

 Steadily increasing quantities of saturated warmer air, then the warm- 

 iug of the mixture proceeds more rapidly at first than subsequently, 

 whereas in the reverse process cooling proceeds more slowly at first 

 and then steadily faster. The quantity condensed has also a similar 

 relation ; it also attains its maximum when there is an excess of the 

 cooler component. 



" TJierefore condensation hepins sooner ichen a jet of cold moist air pen- 

 etrates a large mass of warmer air than when a jet of warin moist air is 

 blown into cooler air.''^ 



Therefore by the outward appearances of clouds that are forming 

 and dissolving in this manner, one perceives whether warmer or colder 

 air predominates. 



From all the preceding we conclude that the following forms of fog 

 and clouds may be considered as originating by mixture : 



(1) The fog above warm moist surfaces, under the intiuence of colder 

 air, therefore especially the fog over the sea in the cold season of the 

 year or during the occurrence of cold winds. 



(2) The "rank and file" clouds occurring on the boundary between 

 two different strata of air flowing rapidly above each other, which von 

 Helmholtz* has first recognized as a consequence of wave motion and 

 designated by the name, atmospheric billows, in which however adia- 

 batic condensation also comes into consideration at i)laces where the 

 air is thrown upward after the manner of the formation of crests and 

 foam on ocean waves. 



(3) The layers of stratus that also form at such separating surfaces 

 and which frequently first appear as atmospheric billows and subse- 

 quently become denser. 



(4) Cloud streamers that form and again dissolve at the summits of 

 mimntains or in narrow mountain passes when the form of the moun- 

 tain is such as to make it possible for jets of warmer or colder masses 

 of air to penetrate into similar masses of other temperatures.t 



(5) The ragged clouds, or the disconnected clouds, such as one fre- 

 quently observes during rapid motions of the air, perpetually changing 



* Sitzungsherichle, Eonig. Preus. Akad. Wissensch . zu Berlin : Berlin, 1888, p. 661, and 

 1889, p. 503. [See also Nos. VI and VII of this collection.] 

 t Von Bezold, Himmel nnd Erde, 1889, vol. 11, p. 7. 



