[ 46 ] 



VII. Amount of Carbon Dioxide in the Atmosphere. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IN the ' Philosophical Magazine' for November 1882, p. 388, 

 Mr. Ernest H. Cook, in his paper on " Carbon Dioxide 

 as a Constituent of the Atmosphere," has fallen into numerical 

 errors in estimating the total amount of C0 2 existing in the 

 atmosphere. Inasmuch as these erroneous results do not 

 materially concern his very interesting discussion of the 

 " Sources of Carbon Dioxide," they would not have called for 

 any notice, but for the fact that his figures are put forward as 

 corrections of the estimates made by his predecessors. I have 

 not been able to discover the precise source of his errors in 

 numbers ; but they seem to have originated in the " cubic 

 mile " estimates. It may be worth while to indicate the me- 

 thod of obtaining the correct numbers. 



Let a = equatorial radius of the oblate spheroid; 



b = polar „ „ „ ; 



h = height of homogeneous atmosphere enveloping it. 

 Then 



volume of spheroid + volume of homogeneous atmosphere 



= |7rx + /i) 2 x (b + h) ; 

 volume of spheroid or earth, 



=|7rxa 2 + 5. 



Taking Bessel's values of a and b for the terrestrial oblate 

 spheroid, and assuming h= 7990 metres (Phil. Mag. 4th series, 

 vol. xxvii. p. 16, Jan. 1864), we have 



a = 6377398 metres, 

 b = 6356080 „ 

 h = 7990 „ 



Hence it follows: — Cubic metres. 



vol. of earth + vol. of homog. atmos. = 1,086,921,403,060 x 10 9 



„ „ itself = 1,082,841,791,538 xlO 9 



.*. vol. of homogeneous atmosphere = 4,079,611,522 x 10 9 

 If we assume the C0 2 in the air == 4 vols, in 10,000 we have 

 volume of C0 2 = 1,631,845 x 10 9 cubic metres or kilolitres. 

 Now, as a cubic metre of C0 2 (density = 1*5291, air = 1) at 

 Paris, under standard conditions, weighs" 1*977467 kilo- 

 gramme, 



.*. weight of C0 2 in atmos. = 3,226,917 x 10° kilogrs. 



