CLXXXVIII. GAUGING OF FLOW OF STREAMS AND ARTESIAN BORKES, 
disadvantages of the current meter are few. It cannot be 
used where there is much floating weeds or grass. It 
requires rating before use and frequently afterwards. It 
must be used with care. But it gives integrated or mean 
velocity. It can be used on streams of all sizes. Gaugings 
can be taken with more rapidity and accuracy than with 
rods, and they are cheaper in the end, as fewer men are 
necessary. ‘The meter adopted by the department was 
originally intended to be fixed on a metal rod so that it 
could be held rigidly, but the author has had a few alter- 
ations made so that it can be suspended by the insulated 
copper wires. The meter is entirely free to turn in any 
direction, the screw being kept facing upstream by a four 
blade tail. The meter is kept from being swept down stream 
by leaden weights, which vary according to the velocity. 
This is a very convenient arrangement, as the meter can 
be raised or lowered very quickly to any desired position 
on the vertical. 
It is open to only one objection, and that is, it is uncer- 
tain whether it is exactly normal to the plane of the section, 
but the meter always has a slight sway backwards and 
forwards through a small angle, and according to Professor 
Unwin'—"* Supposing it to sway backwards and forwards 
through an angle of 40° the error of observation due to its 
position would not exceed 3 per cent.’’ From observations 
by the author when possible, the angle of sway was more 
likely from 5° to 10°. At arecent test of two new meters 
on the Sydney Water Supply Upper Canal, the author used 
a suspended meter without any loading weights, so that 
the meter was swept back a little by the current, yet the 
discharge computed from his observations only differed 
from one by Mr. Surveyor Shute, taken with meter held 
rigidly at the same time by 1°7/, and from one by Mr.. 
Surveyor White by 1°1%, also with meter held rigidly. 
' Proc. Inst. C.E., Vol. uxx1., p. 41. | 
