ORGANIC CHEMICAL AGENCIES. 295 



I have frequently observed during rains, especially when there has been 

 ■a shower on a hot day, that the water flowing from such surfaces is de- 

 cidedly hot, but I never made any record of its temperature. This tem- 

 perature can only be inferred from the data given for the temperatures to 

 w^hich the exposed rock surfaces are subjected. 



Caldcleugh says, however, that the temperature of water running over 

 these exposed rock surfaces " often reaches 140° or 150° Fahrenheit,'' and 

 he believes that the silicious stalactites found by him at Rio de Janeiro 

 were dissolved by these hot waters from the gneiss.* 



For convenience sake chemical agencies may be classed as organic and 

 inorganic. By far the more important of these are the organic acids 

 which are washed over the rocks and soil and into their crevices. These 

 acids are derived from two sources, namely, from burrowing animals and 

 from plants. 



Burrowing animals. — Ants. Most of the burrowing in Brazil is done by 

 ants, termites and other insects.f An important part of the work of these 

 insects is mechanical, but their chemical work is vastly more so. They 

 are found almost everywhere — in fields, forests and campos — though 

 they are much more abundant in some places than in others. 



In some of the campo regions of the Amazon valley of Minas, Goyaz 

 and Matto Grosso the soil looks as if it had been literally turned inside 

 out by the burrowing of ants and termites. 



Forel says that " the ant fauna of South America is perhaps the richest 

 in the world." J 



I do not know how many species of ants and termites live in the ground 

 in Brazil ; § indeed the number of species is a matter of little or no im- 

 portance as compared with the number of individuals and their habits, 

 and of this it is itnpossible to give more than a very general impression* 

 At the time of mating I have often seen the country covered for miles so 

 thickly with young females that they would average an individual to 

 every square yard of surface. 



Of the ants proper there is one kind, known in Brazil as saubas or 

 sauvas, which deserves special attention. 



These ants live in large, often enormous, colonies,! | burrow in the 

 earth, where they excavate chambers with galleries which radiate and 



* On the geology of Rio de Janeiro. Alexander Caldeleugh. Trans. Geol. Soc. Lond., 2d ser., vol. 

 ii, 1829, pp. 69-72. 



t Earthworms, which play so important a part in the formation of soil in temperate climates, take 

 no such part in the work in Brazil. 



I A fauna das formigas do Brazil. Relo Dr A. Forel. Boletim do Museu Paraense, i, 2, p. 89. 

 Para, 1895. 



§ Four hundred and forty species of ants alone are described from Brazil. These are not all bur- 

 rowers, however. Boletim do Museu Paraense, l,no. 2, p. 142. 



II Azevedo Sampaio estimates some of the colonies at 175,000 to 190,000 individuals, and others at 

 600,000. Sauva ou Manhu-uara, pp. 50, 54. Sao Paulo, 1894. 



