44 
fit closely, tor the liquid works through win. re water would not. 
The reservoir can be made larger or smaller, and the lower portion 
which is inserted >n the ground can be made of any length to suit 
the depth to whiji it may sometimes be necessary to apply the 
liquid. On larger instruments a foot-rest could be easily attached 
to assist in inserting the instrument if necessary. The reservoir in 
our instrument (Fig. 18) is 2 feet long, 2>£ inches in diameter, and 
nolds 2 quarts of liquid. 
All the parts of tne i. jector are made of brass or tin except the 
simple discs of leather used in the valves, v. These can be easily re- 
placed when worn. The price at which it can be made and sold will 
depend upon the demand and. also on its size and the material of 
which the reservoir (r) is made, whether tin or brass. The reservoir 
in the one shown in operation in figure 18 is 2 feet long, z'/z inches 
in diameter, and holds about 2 quarts of the liquid. This is about 
the right size for use against the Cabbage Root Maggot, as one fill- 
ing of the reservoir wii treat about 500 plants, using a teaspoonful 
at each plant. It could easily be made larger without adding much 
weight to the instrument, for a slight increase in the diameter of the 
reservoir would greatly increase its capacity. Mr. McGowen can 
make them any size desired. The one shown in figure 18 can be 
made for from * $3 to $5, depending on the demand for it raid the 
material used ; in large quantities they could doubtless be made for 
less. The brass instrument we have has a capacity of two quarts and 
weighs when empty 4^ pounds, and when full of water 4 pounds 
more. Thus, in gardens it will require hut little more than the 
weight of the loaded instrument to force it into the soil. But if a 
larger instrument was needed it might be well to have a foot-rest 
attached near the bottom. 
A few preliminary experiments in cages here at the inseclary 
with this substance showed that it killed, not only the maggots, but 
the puparia also. Scarcely a live insect could be found in the cages 
the next day after applying a teaspoonful of the liquid to each plant. 
Ten puparia were placed beneath the soil in each of two cages, and 
to one cage a teaspoonful of the liquid was applied and the other 
was left untreated. No flies ever emerged in the treated cage, while 
nearly every one of the puparia gave out a fly in the untreated cage. 
In no case did the plants show any signs of injury from the liquid. 
We alwdys applied the liquid in a horizontal hole beginning about 
three or four inches from the plant and running down to a point a 
little below the roots. 
But while our experiments demonstrated that the substance was 
sure death to the insects and did not injure the plants, we were con- 
* Since making a quantity of them Mr. r.icGowan has found it ueccessary 
to make the price $ 7.00 each. 
