280 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



half stopping in the upper chamber of the c^^Hnder, 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 tbau 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 j or (3) the upper half of the 

 cylinder may have an inside capacity equal to one-half the inside capac- 

 ity of the lower half of tbe 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 cyliuder, having both suction and discharge at each 

 end; or (6) 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 ^o. 7 has been described as seen in 

 Plate XL, Fig. 4, as the "Hydropult" of Mr. W. T. Yose, of Boston, 

 Mass. The plan ^o. G is illustrated in an air-pump contrived by my- 

 self, described as shown in Plate XXXY, Fig. 1. The pumps on the 

 No. 5 phm, as heretofore made, are uot simple enough to be practical 

 in the work here under consideration: Those of No. 4, which have the 

 twocylinders 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 desira,ble for the work in 

 question, yet one of these which will answer the x>urpose is represented 

 in Plate XLY, Fig. 4, and deserves more special notice. 



The Champion Force pump. — Is manufactured by the Champion Iron 

 Fence 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, hj bearing cylinder, b, which opens above into the base of the 



