the several Gases in the Atmosphere. 3.33 



f . Of the IVeight of the Aqueous Vapour Atmosphere. 



1 have, in a former essay, (Manchester Mem. vol. v. 

 p. 2, page 359,) given a table of the force of vapour in 

 vacuo for every degree of temperature, determined by ex- 

 periment, and in the sequel of the essay have shown that 

 the force of vapour in the atmosphere is the very same as in 

 vacuo, when thev are both at their utmost for any given 

 temperature. To find the force of aqueous vapour in the 

 atmosphere, therefore, we have nothing more to do than 

 to find that degree of cold at which it begins to be con- 

 densed, and opposite to it in the table above mentioned 

 will be found the force of vapour. From the various facts 

 mentioned in the essav, it is obvious, that vapour con- 

 tracts no chemical union with any of the gases in the at- 

 mosphere; this fact has since been enforced in the Aunales 

 de Chimie, vol. xlii. by Clement and Desorme. 



M. De Saussure found by an excellent experiment, that 

 dry air of 64" will admit so much vapour as to increase its 

 elasticity -Jyth. — This I have repeated nearly in his man- 

 ner, and found a similar result. But the table he has given 

 us of aqueous vapour at other temperatures is very far 

 wrono:, especiallv at temperatures distant from 64''. — The 

 numbers were not the result of direct experiment, like the 

 one above. — If we could obtain the temperatures of all 

 j):irls of the earth's surface, for any given time, a mean of 

 them would probably be 57° or 58". Now, if we may sup- 

 pose the force of vapour equivalent to that of 55", at a 

 medium, it will, from the table, be = to •443 of mercury, 

 or nearly yV'h of the whole atmosphere. This, it will be 

 perceived, is calculated to be the weight of vapour in the 

 whole atmosphere of the earth. If that incumbent over 

 any place at any time be required, it may be found as di- 

 rected above. 



3. Of tJie IVeight of the Carbonic Acid Atmosphere. 



From some observations of Humboldt, I was led to ex- 

 pect about -i-iro'^''^ \>^^^ o^ '■lis weight of the atmosphere to 

 he carbonic acid gas : but I soon hnmd that the proportion 

 was inmicnscly o\crrated. From repeated exporim.ents, all 

 nearly agreeing in then- re^^ults, and niade at different sea- 

 sons of the year, I have I'ound, that if a glass vessel filled 

 1^ilh 102,400 grains of rain water be einpiicd in the open 

 air, and 195 grains of strouii lime water be poured in, and 

 the mouth then closed; by sufficient time and agitation, 

 the whole of the lime water is just saturated by the acid 



Vol. 23. No. y-j. Jan. 1806. Z gas 



