SCIENTIFIC BALLOON ASCENSIONS VON BEZOLD 317 



throughout the atmosphere and lead to the agreeable conviction 

 that the observations already given by balloon voyages as to con- 

 ditions prevailing in the atmosphere apply to a very considerable 

 fraction of the whole atmosphere. 



They also Show what an important part the lower and best known 

 strata plays with reference to the economy of heat in the atmosphere. 

 In all ascensions above 3300 meters and for the average distribution 

 of temperature, we have already surmounted one-third of the 

 whole atmosphere and in the ascensions of sounding balloons above 

 8400 meters we have passed through two-thirds of the atmosphere. 



Furthermore, one sees quite vividly how rapidly the quantities 

 of heat diminish with the altitude, which fact comes in play when 

 equal changes of temperature occur in high and low strata, and we 

 see how erroneous it is to replace the clearly defined expression 

 "Temperature of the air" by that of "Atmospheric heat." 



In order to warm by i° C. a definite given volume of air or a layer 

 of air of definite thickness at the surface of the earth, there is needed 

 twice as much heat as under average conditions is needed at the 

 altitude of 5000 meters. Equal oscillations of temperature in the 

 upper and lower strata which one naturally assumes to be of equal 

 mass, i. e., of equal altitude, will therefore have much less importance 

 in the former than in the latter. Moreover, the expression "Distri- 

 bution of heat over the surface of the globe," which is generally 

 used and therefore not easily abolished, is, strictly speaking, not 

 correct, since we do not really mean the distribution of heat, which 

 depends not only on the density but also on the moisture of the air, 

 but we have in mind only the distribution of the temperature at a 

 few meters altitude above the ground. 



The diagram, fig. 47, is now easily understood, especially when we 

 add that the full horizontal lines refer to the scale of barometric 

 pressures given on the left, while the dash lines refer to the scale ot 

 altitudes given on the right hand of the diagram. 



If we consider the vertical line belonging to the temperature — 6o°C. 

 as the axis of ordinates then the abscissae of the curve of condition 

 / m are directly proportional to the quantities of heat that must be 

 given to a unit mass of air having the pressure given at the left-hand 

 in order to warm it from the temperature — 6o° C. up to that of / m . 



In a corresponding way the abscissae of the curve >" m give the grams 

 of water contained in a kilogram of air of the corresponding stratum; 

 the abscissae of the curve y s give the grams of water that would be 

 contained in this kilogram of air if it were perfectly saturated. The 

 number of grams is inscribed at the top of the diagram, fig. 47 



