262 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



unci requiring no dead points in tlieir operation they would be desirable 

 especially in large horse-power machines, j'et I think the general results 

 of past experience with them for other purposes shows that they are 

 less durable than the common reciprocating x)istoned pumps. 



HYDRAULIC BELLOWS. 



The hydraulic bellows are closely related to oscillating pumps, but do 

 not require the i^ackings which are necessary to the latter, and there is 

 less friction in their working. These are very simple instruments for 

 ejecting liquids. They are really simpler than most pumps. Yet, here- 

 tofore, they have generally not proved preferable, chiefly from weak- 

 ness or imperfection of construction, or from lack of durability of the 

 materials in their composition. The faults of constiuction are over- 

 come by the methods of bellows construction which I have designed 

 and tested as set Ibrth in another part of this work. The materials can 

 be protectively treated, and hence the use of a small hydraulic bellows 

 immersed in a tank or barrel, or other vessel, is a very simple and prac- 

 tical device for distributing liquids. 



OSCILLATINa FORCE-PUMPS. 



The oscillating force-pump proper has for its chamber a radial seg- 

 ment of a cylinder. In it a radial septum or one of its radial sides is 

 made to oscillate, or the chamber itself may oscillate when the other 

 part is fixed. The motion is solely one of reverting partial rotation of 

 either the piston or its chamber with reference to the other. The 

 oscillating relation is between the piston and its encasement. This de- 

 finition precludes many falsely so-called '' oscillating pumps," in which 

 the oscillation is not between the piston and its chamber. It precludes 

 all true, straight cylinder pumps. I have tested only one pum^) of this 

 group suitable for use in ejecting poison. It is patented by A. G. Brust 

 and W. H. Douglas, of Washington, D. 0. The latter gentleman is its 

 manufacturer. 



RECIPROCATINa FOR(.'E-PUMPS. 



These are most conveniently considered under four headings: «, Hy- 

 dronettes and Fountain pumps ; &, Bucket pumps and Knapsack pumps ; 

 c, Aquapults, &c.; fZ, Barrel and Tank pumps. 



HyDRONETTES AND FOUNTAIN PUMPS (PlatCS XXXVIII, XXXIX, 



XL, XLI, and XLIV). — Certain hand-pumps known to the trade under 

 the above names are capable of very general a|>plication to purposes 

 for which other special forms of pumps and syringes are used. They 

 deserve the following notice respecting their use in the tillage of cot- 

 ton, &c.: 



The double-acting, hand force-pumps that discharge through a piston - 

 tube or hollow i)iston-rod, which has an outside cai>acity equal to one- 



