152 Woo Go LRIRAUINIMIGIR, 
In the vicinity of the city of Theophilo Ottoni there are 
several old fields apparently abandoned to the ants. The 
accompanying plate is from a photograph taken on the slope of 
the hills west of the railway station at this city. The mounds 
here are all low and rounded as if they were old. 
I regret that this picture does not give a better idea of the 
size and abundance of the ant-hills; unfortunately it was taken 
when the sun was 
almost directly 
overhead,and the 
view is up the 
slope and along 
themside on mtic 
hill Beronemtne 
photograph was made the man in foreground was sent behind 
Ant-hills in an old field on the Rio Mucury, State of 
Minas Geraes, Brazil. 
the hill at the foot of which he sits, but though he was over six 
feet high I could only see the top of his hat. The black lumps 
shown are hard masses weathered from the large mounds. 
In the city of Theophilo Ottoni the streets are cut down in 
many places through the rock decayed in places. In some of the 
fresh cuts I observed the holes made by ants penetrating the 
ground in one place to a depth of ten feet, in another to a depth 
of thirteen feet, below the surface of the ground; many others 
were seen at a depth of six, seven and eight feet below the sur- 
face. 
It goes without saying that the ants do not bore into the hard 
undecayed rocks, but it seems reasonable to suppose that the 
opening up of the ground by their long and ramifying under- 
ground passages hastens decay, and that the working over of 
the soil must contribute more or less to the same end. 
The impression one gets from the work of the ants along the 
line of the Bahia and Minas railway —and for that matter in any 
other part of the tropics—is that they are vastly more important 
as geologic agents than the earthworms of temperate regions. 
Since the publication of my paper upon the decomposition of 
rocks in Brazil, in which several writers are quoted upon the work 
