in the Air upon the Temperature of the Ground. 245 



creases in intensity in the proportion 1 : 0'934 (log= — 0'0296), 

 the corresponding value for the unit of water-vapour is 

 1 : 0*775 (log = —0*1105). These figures are of course only 

 valid for the circumstances in which the observations were 

 made, viz., that the ray should have traversed a quantity of 

 carbonic acid K = l'l and a quantity of water-vapour W = 0'3 

 before the absorption in the next quantities of carbonic acid 

 and water-vapour was observed. And these second quantities 

 should not exceed K = l'l and W = l*8, for the observations 

 are not extended over a greater interval than between K = l*l 

 and K = 2'2, and W = 0*3 and W = 2'l (the numbers for K 

 and W are a little different for rays of different kind) . Below 

 A is written the relative value of the intensity of radiation 

 for a given kind of ray in the moonlight after it has traversed 

 K = l and W = 0*3. In some cases the calculation gives 

 positive values for log x or log y. As this is a physical 

 absurdity (it would signify that the ray should be strength- 

 ened by its passage through the absorbing gas), I have in 

 these cases, which must depend on errors of observation, 

 assumed the absorption equal to zero for the corresponding- 

 gas, and by means of this value calculated the absorption- 

 coefficient of the other gas, and thereafter also A. 



As will be seen from an inspection of Table I., the values of 

 i obs. agree in most cases pretty well with the calculated values 

 i calc. But in some cases the agreement is not so good as one 

 could wish. These cases are mostly characterized by a small 

 " weight " G, that is in other words, the material of observa- 

 tion is in these cases relatively insufficient. These cases 

 occur also chiefly for such rays as are strongly absorbed by 

 water-vapour. This effect is probably owing to the circum- 

 stance that the aqueous vapour in the atmosphere, which is 

 assumed to have varied proportionally to the humidity at the 

 earth's surface, has not always had the assumed ideal and 

 uniform distribution with the height. From observations 

 made during balloon voyages, we know also that the dis- 

 tribution of the aqueous vapour may be very irregular, and 

 different from the mean ideal distribution. It is also a 

 marked feature that in some groups, for instance the third, 

 nearly all the observed numbers are less than the calculated 

 ones, while in other groups, for instance the fourth, the 

 contrary is the case. This circumstance shows that the division 

 of the statistic material is carried a little too far ; and a combi- 

 nation of these two groups would have shown a close agreement 

 between the calculated and the observed figures. As, how- 

 ever, such a combination is without influence on the correct- 

 ness of the calculated absorption-coefficients, I have omitted 



