Atrnospherkal Phcenomena. 245 



attention of mankind, but still more the changes which take 

 place in the same place, — the oscillations of the mean relations 

 of the weather. There is no portion of human knowledge in 

 which we find so many more or less different or contradictory 

 views as in meteorology, and the phenomena themselves are 

 more complicated than in almost any other department of the 

 natural sciences; the appearances which succeed one another stand 

 in such intimate connection, that the very one which was the con- 

 sequence of previous phenomena becomes also the cause of future 

 variations ; and hence it happens that the weather, which we re- 

 mark at any moment at the place we inhabit, is not only acted 

 on by causes which are in activity at one particular position, 

 but also that the weather of every other portion of the earth ex- 

 ercises a greater or less influence on it. The great multitude of 

 elements, which must be kept in view according to what we have 

 just said, increases to a great extent the difficulty of investigat- 

 ing the isolated phenomena; and although during the last 

 twenty or thirty years treatises have appeared, which in excel- 

 lence leave far behind the works of the earlier natural philoso- 

 phers, yet we ought only to regard the results obtained, as the 

 foundations of a building, which still remains to be erected in 

 due and harmonious proportions in time to come. The object 

 of the following pages is to communicate the more important 

 meteorological laws, and I hope they may have the effect of ex- 

 citing natural philosophers more and more to continued obser- 

 vations, and to the publication of the laws deduced from them. 

 Temperature of the Atmosphere. — The most important cause 

 of all meteorological phenomena is the sun, and this is owing 

 to the warming power of its rays ; were the sim merely 

 an attracting body without luminous rays, the temperature 

 of the whole earth would be equal, and the alternation of 

 heat and cold in the course of the day and the year would 

 disappear. The intensity of the action of the sun is not 

 alike every-where or even at the same place at different times, 

 inasmuch as that depends on the height of the heavenly body 

 above the horizon of the place of observation. If we imagine 

 a cylindrical bundle of parallel rays of the sun, it will possess 

 at all times the same heating power ; if we intersect it by plane 

 surfaces under different angles of inclination, the cutting sur- 

 face is the smallest when it stands at right angles to the axis of 



