in the Air upon the Temperature of the Ground. 265 



By means of these values, I have calculated the mean 

 alteration of temperature that would follow if the quantity of 

 carbonic acid varied from its present mean value (K=l) to 

 another, viz. to K = 067, 1*5, 2, 2'5, and 3 respectively. This 

 calculation is made for every tenth parallel, and separately 

 ~for the four seasons of the year. The variation is given in 

 Table VII. 



A glance at this Table shows that the influence is nearly 

 the same over the whole earth. The influence has a minimum 

 near the equator, and increases from this to a flat maximum 

 that lies the further from the equator the higher the quantity 

 of carbonic acid in the air. For K = 0'67 the maximum 

 effect lies about the 40th parallel, for K = 1'5 on the 50th, 

 for K = 2 on the 60th, and for higher K- values above the 

 70th parallel. The influence is in general greater in the 

 winter than in the summer, except in the case of the parts 

 that lie between the maximum and the pole. The influence 

 will also be greater the higher the value of v, that is in 

 general somewhat greater for land than for ocean. On account 

 of the nebulosity of the Southern hemisphere, the effect will 

 be less there than in the Northern hemisphere. An increase 

 in the quantity of carbonic acid will of course diminish the 

 difference in temperature between day and night. A very 

 important secondary elevation of the effect will be produced 

 in those places that alter their albedo by the extension or 

 regression of the snow-covering (see p. 257), and this secondary 

 effect will probably remove the maximum effect from lower 

 parallels to the neighbourhood of the poles *. 



It must be remembered that the above calculations are 

 found by interpolation from Langley's numbers for the values 

 K = 067 and K=1'5, and that the other numbers must be 

 regarded as extrapolated. The use of. Pouillet's formula 

 makes the values for K = 0*67 probably a little too small, 

 those for K = 1'5 a little too great. This is also without 

 doubt the case for the extrapolated values, which correspond 

 to higher values of K. 



We may now inquire how great must the variation of the 

 carbonic acid in the atmosphere be to cause a given change of 

 the temperature. The answer may be found by interpola- 

 tion in Table VII. To facilitate such an inquiry, we may 

 make a simple observation. If the quantity of carbonic acid 

 decreases from 1 to 067, the fall of temperature is nearly the 

 same as the increase of temperature if this quantity augments 

 to 15. And to get a new increase of this order of magnitude 

 (3° # 4), it will be necessary to alter the quantity of carbonic 

 acid till it reaches a value nearly midway between 2 and 2*5. 



* See Addendum, p. 275. 



