576 Wisconsin Academy of Sciences , Arts , and Letters. 
under the cone and projects through its apex in a small loop 
to which the line is attached. The cone consists of brass 
wire netting with a 2 mm. mesh. It has a slant height of 
about 9 cm. At the base, this netting is soldered to the 
upper edge of the copper band and at the top to the wire 
loop. Two loops of wire are soldered to the copper band 
from which lines pass to similar loops on the bottom part of 
the net. 
Fig 4.—Metal parts of Birge cone net. 
The bottom of the net (fig. 4, B) consists of a tube of 
sheet copper, about 3 cm. in diameter, and 3.5 cm. long, to 
the lower end of which is soldered the screw top of a kerosene 
can. A small brass wire is soldered around the upper edge 
of the tube, thus forming a rim which enables one to tie the 
lower end of the cloth net to the bottom more securely. 
Toward the lower end of the tube there are two small loops 
of wire, to which lines from the top are attached. These 
lines are a little shorter than the cloth part of the net and 
thus carry the weight of the bottom. A piece of lead is 
soldered to the screw cap of the can top, and this extra 
weight causes the bottom to sink promptly so that the air 
