PAPER BY PROF. BEZOLD. 285 



of condensation and of dissolution, that is to say, between the ordiuates 

 2/i* and y 2 *, then will the resulting mean temperature t=^ 1 * be 



attained quicker when we go from y v * towards y 2 * than when we go 

 from y 2 * towards #,*. For since t > t 3 therefore for t = £ (£i*+<2*) the 



mixing-ratio 1 > 1, that is to say, the mixture shows the average 

 m 2 



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 



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



whereas in the reverse process cooliug proceeds more slowly at first 



aud then steadily faster. The quantity condeused has also a similar 



relation ; it also attaius its maximum wheu there is an excess of the 



cooler component. 



" Therefore condensation begins sooner when a jet of cold moist air pen- 

 etrates a large mass of warmer air than when a jet of warm 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 

 ail 1 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 influence of colder 

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

 year or during the occurrence of cold winds. 



(2) The "rank and file 1 ' 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 places 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 aud subse- 

 quently become denser. 



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

 mountains or in narrow mountain p sses'when the form of the moun- 

 tain is such as to make it possible lor 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 



* Sitzungsberickte, Konig. Preus. Akad. Wisstnsch . sn Berlin : Berlin, 1888, p. GG1, ami 

 1889, p. 503. [8re also Nos. VI and VII of this collection.] 

 t Von Bezohl, Himmel und Erde, 1889, vol. II, u. 7, 



