280 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
half stopping in the upper chamber of the cylinder, which is reduced 
one-half by having a lesser diameter or an enlarged piston-rod, while 
the other half of the liquid is discharged. On the next or upward 
stroke the half that remains above is discharged while the cylinder is 
being filled from below. Thus the discharge is one-half at each stroke 
while the suction is all at alternate strokes. Attempts thus far made 
to produce suction at both strokes add more complication or inconven- 
ience of form to the pump than the gain thereby will compensate. 
The reduction for semi displacement in these pumps is commonly ac- 
complished in one of the following ways: (1) The piston-rod has an out- 
side capacity equal to one-half of the inside capacity of the cylinder ; or 
(2) there may be a median packing septum, and the upper half of the 
plunger has an outside capacity equaling one-half of the outside ca- 
pacity of the lower half of the plunger ; or (3) the upper half of the 
cylinder may haye an inside capacity equal to one-half the inside capac- 
ity of the lower half of the cylinder, in which case two oppositely work- 
ing piston-heads are used in the respective halves and the cylinder 
discharge is from a median point; or (4) two cylinders of equal size are 
used, standing end to end, side by side, or otherwise, with their pistons 
acting oppositely or alternately to discharge through the same spout, 
in which cases one cylinder, may discharge through the other, or two 
separate confluent spouts maybe employed for the outlet; or (5) a single 
piston with a single cylinder, having both suction and discharge at each 
end; or (0) an arrangement providing suction at both ends and discharge 
from the piston at one end; or (7) the suction is between the excurrent- 
valved pistons working together simultaneously in a U-shaped cylinder 
supplied at one end or at the middle. 
A pump arranged on plan No. 7 has been described as seen in 
Plate XL, Fig. 4, as the "Hydropult" of Mr. W. T. Yose, of Boston, 
Mass. The plan No. C is illustrated in an air-pump contrived by my- 
self, described as shown in Plate XXXV, Fig. 1. The pumps on the 
No. 5 plan, as heretofore made, are not simple enough to be practical 
in the work here under consideration. Those of No. 4, which have the 
t wo cylinders with contiguous axles, cannot be satisfactorily used except 
in wells, &c; also those with two cylinders side by side and with alter- 
nating pistons are too complex and lack compactness, while those with 
two cylinders out of line and the top of the suction cylinder discharg- 
ing into the base of the discharge cylinder likewise exhibit rather 
more complication and friction than seem desirable for the work in 
question, yet one of t^ese which will answer the purpose is represented 
in Plate XLV, Fig. 4, and deserves more special notice. 
The Cha in ]) ion Force pump. — Is manufactured by the Champion Irou 
Pence Company, Kenton, Ohio, and can be sold at a moderate price. 
In the figure the pump cylinders, a b, are represented as opened 
upon one side to show the interior parts. Below is seen the suction 
pipe, fc, bearing cylinder, 6, which opens above into the base of the 
