HYDROGRAPHY. 83 
mainly for storage projects the stations are so located that both the 
high-water and the low water conditions can be studied with equal 
accuracy. The equipment at the stations consists of a gage for meas- 
uring heights of the water surface, and some support from which the 
meter measurements can be made. 
The gage is either a fixed wooden staff or is of the standard chain 
type. Gage heights are read daily by some person living in the 
vicinity, who is employed for the purpose, and the records are trans- 
mitted to the resident hydrographer on postal-card forms prepared for 
that purpose. 
Measurements of the flow or discharge are made with current 
meters from a bridge, boat, cable, or by wading. (See PI. VII.) 
Whenever possible, stations are established at bridges, where stations 
can be equipped at little expense. The measurement, which is usually 
made by the resident hydrographer or an assistant, consists in dividing 
the cross section of the stream at the gaging station into an arbitrary 
number of parts and determining the area and mean velocity for each 
part; the product of these two factors gives the discharge for each 
part, and the total discharge is the sum of these partial discharges. 
An effort is made to take the measurements at different stages, so that 
when they are plotted on cross-section paper enough points will be 
had to construct a discharge curve that will extend from extreme high 
to extreme low water. 
Aside from the meter stations, a few determinations of flow are 
made by small weirs and at mill dams. 
The current meter is an instrument for determining the velocity of flow 
of streams. In general it consists of a wheel carrying a series of cups 
which rotate about a horizontal or a vertical axis. Connected with 
this axis is either an electric or an acoustic appliance for counting the 
number of revolutions. The velocity per second is indicated by the 
number of revolutions per second. This relation is determined sepa- 
rately for each meter by drawing the meter through still water. The 
length and time of the run and the number of revolutions are recorded 
by automatic devices, and from these factors the velocity in feet per 
second, to correspond to any number of revolutions, is determined. 
PI. VIII, A, shows the equipment at meter-rating stations. In opera- 
tion the meter is held in the water and headed against the current, 
which causes the wheel to rotate. Since the organization of the work 
five types of meters have been used — Fteley, Ellis, Haskell, Bailey, 
and Price. Each of these has its good points, but the Price meter best 
fulfils the demands of the work and is in general use. 
The Price meter is made in two sizes. It consists of a wheel contain- 
ing five conical cups, rotating about a vertical axis, which is connected 
by a copper-wire cable to a small battery buzzer, and is so arranged 
as to make and break contact with each revolution of the wheel. 
