Attractions and Repulsions of small Floating Bodies. 47 



The foregoing corrected numbers do not differ materially 

 from the rough estimates of Dumas and Boussingault in rela- 

 tion to the volume of the homogeneous atmosphere, and of 

 Roscoe and Schorlemmer in relation to the total weight of C0 3 

 in the air, as cited by Mr. Cook. 



Similarly, if we assume the C0 2 in the air =3 vols, in 10,000, 



.*. volume of C0 2 = 1,223,884 x 10 9 cubic metres or kilolitres, 

 weight of C0 2 =2,420,188 x 10 9 kilogrammes. 



We may estimate the weight of C0 2 in the atmosphere in a 

 much simpler (and scarcely less exact) manner by computing 

 its pressure on a unit surface. Thus, under standard condi- 

 tions, the pressure of the atmosphere on a square metre at the 

 surface of the earth = 10,332*9068 kilogrammes. Assuming 

 the amount of C0 2 in the air = 4 vols, in 10,000, its weight or 

 pressure would be 6*1164 parts in 10,000. Hence the pres- 

 sure of C0 2 on one square metre at the earth's surface is equal 

 to 6*320019 kilogrammes. 



Now the surface of the terrestrial oblate spheroid, of the 

 dimensions above given, = 509,950,861 x 10 6 square metres. 

 Hence the pressure of C0 2 on the entire surface of the sphe- 

 roid = 3,222,900 x 10 9 kilogrammes. 



And, similarly, assuming the amount of C0 2 = 3 vols, in 

 10,000, its weight or pressure would be 4*5873 parts in 10,000. 

 Hence the pressure of C0 2 on the entire surface of the spheroid 

 would be = 2,417,175 X 10 9 kilogrammes. 



I am, yours sincerely, 



Berkeley, California, JOHN LeConte. 



November 30, 1882. 



VIII. Apparent Attractions and Repulsions of Small Floating 

 Bodies. By John LeConte*. 



[Plate I.] 



ALTHOUGH the apparent attractions and repulsions of 

 small floating bodies is one of the most familiar pheno- 

 mena, and one of the earliest to which the physical theory 

 of capillarity was applied, yet it remains a perplexing puzzle 

 to a large number of intelligent students. This arises from, 

 the fact that the popular explanations given in many stan- 

 dard works on elementary physics do not bear a critical exa- 

 mination, and are consequently any thing but satisfactory to 

 the student who endeavours to secure a clear physical concep- 

 tion of the cause of these motions. 



* From Silliman's American Journal for December 1882. 



