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ditches, and it may be used anywhere in pans or in saturated cloths, 
stretched on frames, drawn over the field . The method of using it on the 
irrigating ditches in Colorado is thus reported by Prof. R. L. Packard : 
Jt consists essentially in pouring, or, better, dropping coal tar or coal oil on, the 
running water with which the irrigating ditches, are supplied. The method of sup- 
plying these ditches with oil is very simple. It is only necessary to sprinkle a few 
drops of coal tar on the stream, when the oils contained in the tar are diffused over 
the surface of the water, and coming in contact with the insects (no matter how 
many), cause their speedy death. The toxic power of coal oil upon the insects is 
very remarkable ; a single drop of it floating on the water is capable of causing the 
death of a large number of insects. A simple and ingenious mode of keeping up a 
constant supply of the tar to a ditch I saw exemplified upon the farm of Mr. Arnett. 
A three-quart can is perforated on the side close to the bottom, a chip loosely fitting 
the aperture is inserted therein, and the can is then immersed (by a weight if neces- 
sary) in the ditch. Three quarts or less of tar, trickling out drop by drop from this 
slight vent, are sufficient to keep a great length of ditch supplied with coal oil for 
36 hours. The precise extent of ditch which may thus be rendered toxic to the 
locusts can not, of course, be exactly stated. It is in fact quite indefinite, for the 
reason that the quantity of oil necessary to kill one of the insects is almost infin- 
itesimal, and for the further reason that a single drop of oil will cover quite a large 
surface when dropped on water, so that taking these two facts together, it is easy to 
see that a very small quantity of tar or oil will serve to guard by means of ditches 
a large tract of territory from the ravages of the young (nnwinged) locusts. 
The pans that were used in Kansas and Iowa, but principally in the 
former State, were of very simple construction and very effectual. 
A good and cheap pan is made of ordinary sheet-iron, 8 feet long, 1L 
inches wide at the bottom, and turned up a foot high at the back and 
an inch high at the front. A runner at each end, extending some dis- 
tance behind, and a cord attached to each front corner, complete the 
pan, at a cost of about $1.50. (PI. viii. Fig. 2.) 
We have known from 7 to 10 bushels of young locusts caught with 
one such pan in an afternoon. It is easily pulled by two boys, and by 
running several together in a row, one boy to each outer rope, and one 
to each contiguous pair, the best work is performed with the least labor. 
Longer pans, to be drawn by horses, should have transverse partitions 
(PI. in, Fig. 8) to avoid spilling the liquid ; also more runners. The 
oil may be used alone so as just to cover the bottom, or on the surface 
of water, and the insects strained through a wire ladle. When the in- 
sects are very small, one may economize in kerosene by lining the pan 
with saturated cloth, but this becomes less efficient afterward, and frames 
of cloth saturated with oil do not equal the pans. Where oil has been 
scarce, some persons have substituted concentrated lye, but when used 
strong enough to kill it costs about as much as the oil. The oil pans can 
be used only when the crops to be protected are small. 
Small pans for oil, attached to an obliquing pole or handle, do excel- 
lent service in gardens. 
Mr. A. A. Price, of Eutland, Humboldt County, Iowa, sends the com- 
mission the following description of a coal-oil pan to be drawn on run- 
ners, and which was used with much success in northwestern Iowa (PI. 
vni, Fig. 1) : 
