INFLUENCE OF CABONIC ACID. 



305 



as trustworthy, and in their place we are obliged to use those made by 

 the Transit of Venus Commission of the French Academy in 1882 and 

 1883 at Saint Augustine, Florida; in Haiti, in Martinique, Puebla, Fort 

 Loreto, Mexico, and at Cerro Negro, in Chile. These determinations, 

 while they average a little lower than do those made in Europe, vary 

 only between 2.665 in Chile and 2.897 volumes in 10,000 in Florida. It 

 seems probable, therefore, that while there may be less carbonic acid in 

 the air in the tropics the difference is scarcely perceptible. * 



Fischerf gives several determinations of carbonic acid in rain and snow- 

 water which show that the amount varies much in spite of the constant 

 amount in the air. The carbonic acid in rainwater is between 6.7 and 

 14.1 per cent by volume of all gases found in the water, which is equiva- 

 lent in the cases cited to from 0.22 to 0.45 per cent by volume of water. 



The actual amount of carbonic acid carried down in the rains is deter- 

 mined from these figures and from the rainfall. 



The rainfall at various places in Brazil is given in the table below, and 

 if we assume that the amount of carbonic acid brought down by the rain 

 in Brazil is a mean between the extremes given in the table, or 0.33 J of 

 one per cent by volume (equivalent to .0065 grains in 1,000 by weight) 

 we should have precipitated in the rains the amounts of carbonic acid 

 given in the fourth column. 



Mean annual Rainfall in Brazil.'^ 



Station. 



Rio de Janeiro 



Santos, S. Paulo 



Serra do Cabatao, S. Paulo 



Sao Paulo 



Uberaba 



Morro Velho, Minas 



Gongo Soco, Minas 



Parji 



Ceard, 



Pernambuco . , . . 



Victoria 



Colonia Isabel 



S. Bento das Lages 



Bahia 



Years of ob- 

 servation. 



29 



15 



15 



4 



3 



25 



2 



4 



28 



Rainfall in 

 millimeters. 



974.6 

 2,503.0 

 3,576.7 

 1,494.1 

 1,560.8 

 1,637.0 

 2,939.3 

 1,788.7 

 1,491.5 

 2,971.7 

 1,050.5 

 1,037.0 

 2,179.5 

 2,394.8 



Millimeters 

 of CO, in 

 rainfall. 



3.21 

 8.26 

 11.80 

 4.93 

 5.15 

 5.40 

 9.70 

 5.90 

 4.92 

 9.80 

 3.46 

 3.42 

 7.19 

 7.90 



* Determinations de I'acide earbonique de I'air dans les stations d'observation du passage de 

 Venus. A. Muntz et E. Aubin. Comptes Rendus, 96, 1883, pp. 1793-1799. 



Die Chemische Teehnologie des Wassers. Ferdinand Fischer. Brauschweig, 1880, pp. 75, 76. 



$ This amount is two-tliirds greater than the theoretic amounts given by Roth (Allgemeine und 

 Chemische Geologie. Berlin, 1879, i, p. 44), but inasmuch as they are taken from actual deter- 

 mination it seems best to adhere to Fischer's figures. 



? Die Vertheilung der Regenmengen in Brasilien. Von Professor F. M. Draenert. Meteoro- 

 logische Zeitschrift, Sept., 1886, pp. 381-319. 



