Noes GH OLOGICEAGE NiSeINTT Hy EROPIES 
A FEW years ago in treating the subject of the decomposi- 
tion of rocks in Brazil I spoke of ants as geologic agents worthy 
of consideration’ My claims for these humble workers were 
apparently accepted under protest. With this protest I confess 
I have much sympathy, for if I had not seen with my Own eyes 
so much of these ants and their remarkable deeds I never should 
have believed half the stories told of them. 
Last summer while visiting Brazil again ‘I made a few notes 
upon the ant-hills in the State of Minas Geraes, and took a 
photograph showing the kinds 
of hills so common in certain 
parts of that state. I went into 
the interior at one place by the 
Bahia and Minas railway, An ant-hill at Uruct station, Bahia and 
which, starting from the coast ee ee 
near Caravellas in the State of Bahia, runs to Theophilo Ottoni 
(formerly called Philadelphia) in the State of Minas, a distance 
of 376 kilometers. The first 160 kilometers of the road is over 
campos of hard baked Cretaceous clays with only patches of 
forest here and there. Beyond this the rocks are crystalline, 
mostly gabbros and gneisses, up nearly to the end of the line 
where the rocks are old metamorphic mica schists, itacolumites, 
etc., all deeply decomposed. Shortly after leaving the Creta- 
ceous area my attention was attracted by the big ant-hills in the 
forests. These mounds are from three to fourteen feet high and 
from ten to thirty feet across at the base. The new ones are 
steeply conical and the old ones are rounded or flattened down 
by the weather. In many places these mounds are so close 
together that their bases touch each other. 
About Urucut station (k. 226) the ant-hills are so thick that 
the country looks like a field of gigantic potato hills. 
*Decomposition of rocks in Brazil, by J. C. BRANNER: Bul. Geol. Soc. Amer.» 
1896, VII, 295-300. 
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