142 
Psyche 
[December 
average, in the N. S. than in the E. W. directions; moreover the 
four different angles made by the slopes N. S. E. and W. were 
least in the S. and greater and almost equal in the other three, 
on the average. This indicates a tendency for the south slope 
to be spread out, increasing the angle at the top and the distance 
over the top and diminishing the angle of slope on the south face. 
These fifteen hills were steep cones, the angles at the top 
being small, from 100 to 131 degrees and graphs indicate a norm 
about 120-125. The angles on the W. and E. were similar in 
variation from 26-34 and from 23-42 respectively while the angles 
N. and S. show a wider range, 22-55 and 19-43 respectively. 
Thus the most gentle slope was found on the south face and the 
most abrupt slope, 55 degrees, on a north face. 
The measurements over the top show the mounds to range 
from 31 to 91 inches E. W. and 28 to 92.5 N. S. And curves of 
these measurements show the norm of the N. S. distances to be 
greater than that of the E. W., indicating again that the mounds 
are prevailingly drawn out in the N. S. direction. 
This slight average overgrowth of the southerly exposure 
of many mounds in this Timonium region is due to more work 
being put on that part of the mound and this is very patent in 
some mounds whose northerly sides show but few ants over them 
and even become abandoned to such an extent as to be no longer 
thatched over with a compact layer of earth and organic frag- 
ments, as are the perfect mounds, but are eaten out by the rain 
so that some internal cavities are bared, as in an abandoned 
roofless part of a human dwelling. 
Irrespective of North and South, extra work upon only one 
aspect of a mound is often very patent when the mound is reared 
upon a slope, as often happens in this region of many old open 
mine holes. Here the running of the soil down hill is ever counter- 
acted by the ants placing more particles upon the steep slope till 
the form of the mound departs very greatly from a cone of circular 
base and becomes drawn out like a glacier. Investigation would 
be needed to determine why the ants put more material on the 
side from which it tends most to roll away but this may be con- 
nected with the observed ability of the ants to repair breaches in 
the mound, filling up cavities, and finally reconstructing perfect 
