276 Velocity of Reaction before Complete Equilibrium. 



II. Velocity of Reaction, Complete Equilibrium, and Physical 

 Geography and Meteorology. 



The formation and melting of ice, snow, hail, glaciers, 

 snowfields, &c, the evaporation of water (of the atmosphere, 

 of the sea, rivers, &c), the condensation of saturated vapours 

 (fo water, clouds, rain, dew, &c), the solution and carrying 

 away as well as separation of the solid components of the 

 earth, in short, all the most important phenomena which form 

 the main subject of physical geography and of meteorology, 

 follow in their velocity the law given above 



l = C{t -t)(t-t 0V -hK). 



From the form of the equation it folloivs that all those reactions, 

 even in their pure form, can never reach the point of perfect 

 equilibrium. But, besides, here especially do the phenomena 

 become always more complicated, owing to the interference of 

 oilier factors, such as the cooling or warming of the surrounding 

 temperature. For this nason always only apparent and never 

 real points of equilibrium are reached in nature, therefore all 

 the phenomena in nature never come to a state of perfect resr, 

 but every tiling in nature is in a state of eternal reaction. All 

 the above phenomena must therefore henceforth be considered 

 not only in the light of the theoretical points of equilibrium, as 

 it has been up to the present, but also in the light of their actwil 

 state, in the light of velocity of reaction. This I shall endear on- 

 to do in due course in a future publication. Since the conver- 

 gence-temperature, owing to the continual variations in the 

 surrounding temperature, is continually changing, the appa- 

 rent point of equilibrium of a given system also undergoes 

 continuous variations and shif tings. .In considering the 

 above phenomena die importance of the instability constant K 

 must not be overlooked, because it alone explains how a 

 heterogeneous system can be fomud from a homogeneous one 

 without having it necessary as a condition for such a trans- 

 forming that the newly-formed part should first be present in 

 the system (e. g. it explains why overcooled water separates 

 ice, not only when an ice-crystal is first introduced, and an 

 unstable heterogeneous system is thus first formed, but also 

 why this separation takes place without such a crystal having 

 been introduced, see Part I.). The instability constant, 

 it must be remarked, depends upon a series of factors, 

 internal and external. For instance a supercooled liquid or 

 a supersaturated solution begins to crystallize too early if the 

 liquid is shaken, or if a speck of dust has fallen into it ; the 



