It is due very largely to the numerous designs of steam valves, that difficulty has been encountered in managing single-cylinder pumps as successfully as those of the duplex type, the similarity of construction in the latter type, even in minor details, being much more marked. The successful operation of a pump depends to a great extent upon the intelligence displayed in its management, and an engineer can scarcely hope to obtain quiet and smooth running pumps and freedom from breakdowns and perplexing delays except by a thorough knowledge of the details of construction and operation. It must be remembered that _power pumps_ are to be illustrated and explained in a class entirely excluding _steam pumps_; the latter are pumps in which the moving force is steam. _Electric Pumps_ are properly power pumps in which the moving force is _electricity which is conducted to the pumps by wires_. PUMP PARTS. [Illustration: FIG. 181.] _Water Ends._ There are properly speaking four kinds of water ends to steam and power pumps: 1, A solid plunger, with a stuffing box used for heavy pressings in hydraulic apparatus, or as shown in Fig. 182, for larger plungers. 2, A piston packed with fibrous material within the cylinder. See Fig. 181. The letter P in Fig. 182 and the following cuts indicates the plunger. 3, A plunger packed with a metal ring around the outside, as illustrated in Fig. 183. 4, Two plungers, Fig. 184, connected outside of the cylinder with a stuffing box in two cylinder heads, through which the plungers work. These are more fully explained and illustrated as they occur in many examples as they are referred to in the oncoming chapters of this work. The construction of the water ends of single cylinder and duplex pumps is practically the same; any slight differences which may be found are confined to minor details, which in no way affect the general design or operation of the pump. _The steam or power ends_ of numerous and varied makes of pumps are also as shown in the following pages of this work; all pumps actuated by power—steam, electric, etc.—are possessed of these two distinguishing features—1, a steam or power end, and 2, the water end. NOTE.—This statement has exception in the cases of large pumping engines having a fly wheel or supplemental cylinders attached to an accumulator, in which case the steam is worked expansively. [Illustration: FIG. 182.] [Illustration: FIG. 183.] _The steam end of the ordinary single steam pump, and also of the duplex pump, differs from the steam cylinder of the steam engine in that the former has four ports to each cylinder, i. e., two steam ports and two cushioning ports as shown hereafter in figures._ Under the division of the work allotted to the “Steam Pump” will be found all necessary further notice of the steam ends of Pumps. _Pump Valves._ The valve apparatus is perhaps the most important part of any form of pump and its design has a material bearing upon its efficiency.