SCIENTIFIC BALLOON ASCENSIONS VON BEZOLD 303 



In fact, from the consideration of the average curve with its un- 

 expected slight gradients in the lower portion, that is to say, with 

 its surprising steep ascents, there results at first the most astonish- 

 ing fact that in the general average the influence of the soil makes 

 itself felt in a relative cooling of the lower strata of air. 



This result is in direct contradiction of the older views. Formerly, 

 as already stated, we felt that we must accept some very special 

 assumption in order to explain why the lowest strata of the atmos- 

 phere are warmer than the upper, but today we confront the ques- 

 tion, why the difference in the temperature is not much larger than 

 it is. 



I have already treated this subject theoretically in the above- 

 mentioned memoir, 5 which was published a few weeks ago, and now 

 I will only attempt to briefly repeat the most important points in a 

 less abstract form. 



The explanation is found in one circumstance, namely, the 

 great difference of the influences that the outward and inward radia- 

 tion at the earth's surface exert on the atmosphere; a subject to 

 which Lord Kelvin and H. v. Helmholtz have occasionally referred 

 and which W. M. Davis afterwards treated more thoroughly both 

 in his memoirs on whirlwind storms and also in his admirable "Ele- 

 mentary Meteorology." 



Although the cooling and warming of the surface of the globe 

 stand in a simple antithesis to each other, still the processes by which 

 these influences are transmitted to the air are fundamentally differ- 

 ent; they are processes for which many years ago I introduced the 

 term "limited reversible" or "pseudo-reversible." 



This distinction impressed me still earlier as I investigated the 

 processes in adiabatically ascending and descending currents from a 

 very general point of view. If we consider a saturated ascending 

 current of air we find that the law of diminution of temperature 

 (ignoring the hail stage) remains exactly the same down to an 

 exceedingly small difference, no matter whether the water that is 

 formed falls from the current or is carried along with it. The for- 

 mulae that we apply to the so-called reversible changes of condition 

 apply perfectly to this case. In fact the changes in question remain 

 reversible even to the smallest portions if the water falls away as rain 

 or snow, for the separation never proceeds so rapidly that the pre- 

 cipitation disappears immediately from the neighborhood of (or 

 association with) the mass of air in which it originated. 



6 See No. IX of my collected memoirs, (or No. XIII of this collection of 

 translations) . 



