mology. 269 
sition and the projecting ends 
will rest upon the inner surface 
of the globe, and thus furnish a 
means of support for the appar- 
atus. The lid of the pail, e, 
which forms the bottom of the 
trap, has soldered to its inner 
face a cylindrical tube of two 
inches or a little less in length ; 
between this tube and the rim of 
the lid is put first a layer of 
crystals of potassium cyanide 
and over this a half-inch layer 
of plaster of Paris, which should 
be carefully smoothed down and 
then 
led with 
water to form a hardened crust 
over the top a quarter of an inch 
or a little more in thickness. 
The lid will have to be supported 
in the mouth of the pail in some 
way similar to that illustrated 
by the 
cylindrical tube, g, 
four and one-half inches long is 
made just large enough to fit 
snugly over the tube,/, and a 
hollow cone, h, with a diameter 
of three and a height of two and 
one-half inches is fastened to its 
top. If it is thought desirable a disk, i, about four inches in 
diameter, with a collar,/, may be made to slide up and down 
the tube g. 
The whole inside of this trap, except the lower face of the 
hollow cone, h, should be painted black to allow the prey as 
little light as possible to aid them in making their escape ; and 
the cone, c, should be thickly pierced with small holes one inch 
from the top. It is also well to varnish both sides of the ver- 
tical plate, c, the inside of the funnel, b, and the upper surface 
of the hollow cone, h, to make " Facilis desensus Averni." I 
have substituted glass for tin in the plate, c, as this material is 
probably entirely invisible to insects, they are more likely to 
heedlessly dash against it, while they may flutter about the 
bright tin. But it is much more difficult to fasten to the fun- 
