62 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 
of a fortnight later in the season, will prove an effectual protection to 
trees of all kinds. This can be done at small expense, and will prove 
the salvation of the trees. An apparatus can be readily constructed, 
such as has been used on the grounds of the Department of Agriculture, 
on a sufficiently large scaie to economize time and Jabor. It should con- 
sist of a water tank mounted on a cart and furnished with a strong 
force pump operated by one man and furnished with two sets of rubber 
tubing of a sufficient length (a hose reel can be constructed on top of 
the cart), each hose supported by a bamboo extension pole with a cyclone 
nozzle at tip. With such an apparatus as this three men could drive 
along the streets and thoroughly spray two trees simultaneously; while 
if it were found advisable, four independent tubes and four men to 
work them could be employed with a sufficiently powerful pump, and 
thus expedite the work. The details of the more important devices 
connected with this tank-cart are given in considering the Galeruea. 
The bamboo “extension pole” is used simply to stiffen the rubber hose 
and to enable the operator to elevate the spraying nozzle into the center 
of the tree and spray to aso much greater height. The same result 
can be accomplished by means of a brass rod, in sections, and this has 
the advantage of superior strength, and will consequently carry a 
heavier nozzle or a bunch of nozzles at the end. 
The “Cyclone” or  Eddy-chamber” nozzle (see Fig. 6) is better suited 
for work of this kind on small trees than any yet in use. It is small, 
simple, cheap, will not clog, and ‘gives an admirable spray. A combi- 
nation nozzle may be made of several of these which will be readily 
supported by the section rod and will throw a more profuse spray. 
The arsenical compound known as London purple is, as already 
shown, perhaps preferable to white arsenic or Paris green in that it is 
not so liable to burn the leaves while its color enables one to readily 
distinguish poisoned from non-poisoned trees. Moreover it is very 
cheap. From one-quarter to three-quarters of a pound of this substance 
should be used to a barrel of water, and with this quantity of water it 
is best to mix three quarts of cheap or damaged flour which will serve 
both to render the mixture adhesive to the leaves and also to lessen the 
tendency of the poison to burn the leaves. Three-quarters of a pound 
to the barrel may prove too strong a mixture for delicate and susceptible 
young trees, and it will be best for general application to make the 
amount from three-eighths to one-half pound tothe barrel. Paris green 
will require a somewhat heavier dose—say from one-half to 1 pound 
per barrel of water. 
A number of other means have been tried and are more or less effect- 
ual in destroying these defoliators. Such are theapplication of various. 
other insecticides, particularly an emulsion of milk and kerosene, the 
burning of the webs (in case of the web-worm) by thrusting a lighted 
torch, made of various patterns, into the webs; but after full trial, 
nothing has been found more satisfactory than the arsenical mixtures: 
