ANT STRUCTURES 



469 



part of Minas and Bahia that appear to have reached their full develop- 

 ment range from 1 to 4I/2 meters in height and from 3 to 10 meters in 

 diameter at the base. The biggest of these mounds — ^that is, one 4.5 

 meters high and 10 meters in diameter — contains approximately 117 

 cubic meters of earth. 



Mention has already been made of the abundance and size of the 

 mounds in some parts of the Eio Utinga region, in the interior of Bahia. 

 At one place in this region, where the forests had been cleared away so 

 that the mounds were clearly visible, I selected a spot where they were 

 strikingly abundant, and measuring a space 100 by 100 meters, as nearly 

 as it could be done by pacing, counted the mounds within the area and 

 estimated their heights and diameters at the base. 



The slopes of these mounds vary from less than 30 degrees up to 47 

 degrees, and on some parts of them there are even perpendicular places. 

 It was thought that 38 degrees was a fair average for the ones in this 

 particular area. 



The figures obtained are given in the table below : 



Table of Areas and cubical Contents of Mounds of different Sizes within an Area of 



10,000 square Meters. 

 (All measurements are in meters.) 



Number of 



Diameter 



Area of 

 each in 



Total area 



Height. 



Cubical 



Total con- 

 tents in 



mounds. 



of base. 



square 

 meters. 



meters. 



contents. 



cubic 

 meters. 



1 



15 



176.71 



176.71 



4.5 



265 



265 



2 



11 



95.03 



190.06 



4.2 



133 



266 



6 



10 



78.54 



471.24 



3.9 



102 



612 



8 



8 



50.26 



402.08 



3.1 



51 



408 



12 



7 



38.48 



460.76 



2.9 



37 



444 



5 



6 



28.27 



141.35 



2.3 



21 



105 



4 



5 



19.63 



78.52 



2.0 



13 



52 



7 



4 



12.56 



87.92 



1.7 



7 



49 



8 



3 



7.06 



56.48 



1.2 



3 



24 



Totals, 53 







2,064.82 







2,225 















This estimate makes the area actually covered by the mounds close to 

 one-fifth of the total area under consideration. My notes show that 

 within areas of a few acres the ground covered by the mounds is some- 

 times as high as one-half of the total area. The cubical contents of the 

 mounds, if evenly distributed over the entire 10,000 square meters, would 

 have a thickness of 22.25 centimeters. 



Although the mounds within the area here considered were large, they 

 were not the biggest I have seen, nor do they average as large as can be 



