STANDARD - Survey Instrument Antique Center!

230
Current Meters,
The types of current meters, as shown in Figs. I, II, and III, in our former Catalogues, have been
omitted, owing to the many improvements made and embodied in the Meter, as shown in Figs. IV, V, and
VI, this Catalogue. We are, however, prepared to make to order Current Meter No. Ill, as designed by
Mr. Clemens Herschel, if so desired.
Current Meter No. IV.
The electric form of meter shown in Fig IV is especially adapted for observations
upon large rivers, arms of the sea, etc. It has its registering apparatus above the surface
of the water, or on the bank of a river, and current measurements may be made
with it at any depth, and may be continued for a week, or longer, without stopping, if
desired. Half a dozen or more of these meters may be strung on one and the same vertical
rod or wire, and simultaneous observations then taken of the velocities at different
depths below the surface.
This form was used upon the gauging of the Connecticut River* by General Ellis,
and was designed particularly to avoid the catching of floating substances, such as
leaves and grass, upon either the vanes or the axis, and to render the record of the
instrument independent of the position of its axis with respect to the line of the current,
also, to get less friction upon the axis so as to measure low velocities accurately.
This current meter is constructed upon the principle of Robinson's Anemometer, turning by the difference
of pressure upon opposite vanes of the wheel. The vanes of this meter, however, instead of being hemispherical
cups with a straight stem, are made conical at the ends, and are hollow and taper to the central hub, so as
to offer no obstruction to the slipping off of straws, leaves, or grass, as the wheel revolves. The central hub
is made tapering, so that any object can slide off easily, and it extends over the joints at the ends of the axis,
so as to enclose and protect them from floating substances. The axis runs in iridium bearings. The forward
end of the frame which carries the wheel can be turned and secured in any position, so that the wheel can be
horizontal/vertical, or at any desired angle.
The electrical connection is made by carrying an insulated wire from near the center of the instniment,
where the insulated wire from the battery is attached to it by a binding screw when in use, out to the end of
one arm of the wheel frame, where it ends in a fine platinum wire resting upon a ring in the hub of the whee^.
This ring is made of alternate interchangeable sections of silver and hard rubber, secured in place by screws,
so that their position can be changed to register whole or part revolutions as desired. There is also a socket
and set-screw in the body of the frame near the center, for the return current, which can be carried through a
plain wire slightly twisted around the insulated wire so as to form one cord. If the instrument is run upon a
wire, or has a metallic connection with the surface, the return current can be made through that. A better
method now in vogue is to use a " twin " insulated wire.
The universal motion at the center of the frame and the tail are of the usual construction. This meter
can be used in connection with any apparatus for registering the revolutions of the wheel by the breaks in the
electric circuit.
Price complete, as in Fig IV, with electric register and one battery
etc., packed in three cases, ........
. $195.OO
Price of this instrument without electric register and . . . battery 135.OO
* For further information on this point, see Gen'l G. K. Warren's Report of Surveys and Examinations
of Connecticut River.
We can have this meter, as well as Nos, V and VI, carefully rated at an additional expense offrom
$15.00 to $25.00. Unless ordered otherwise, the instruments will be sent unrated.
Current Meters No. V and No. VI.
This form of Current Meter, invented by Fteley & Stearns,! and illustrated on page
198, is specially adapted for observations upon smaller rivers, streams, conduits, flumes,
etc. The 3% inch wheel has vanes of true standard screw pitch welded to the rim and
axle and is perfectly balanced. All edges are sharp to cut the water to avoid eddies.
Its axle is provided with points of iridium, so as not to be affected by grit in the water
and to run in the bearings with minimum friction. These points, combined with accurate
workmanship and good design, insure a permanent and unvarying rating curve.
The instrument is provided with a registering apparatus, the dial wheels of which
are completely protected by a glass cover readily removable at will. This counting
mechanism is operated by a string, by means of which the dial wheels are thrown in
and out of gear. One short pull throws them in and the next pull throws them out ;
next in, and so on.
Guards placed over this mechanism and the wheel protect them from injury and
floating substances. Those of the wheel are far removed from it to avoid checking the
flow of water.
For more extended observations upon rivers, etc., a separate electric register and
battery, shown on page 232, can be supplied with this instrument.
Price of Current Meter No. V, supplied only with the ordinary
registering apparatus, as shown in the main cut on page 232, and with
12 feet of brass tubing, made in sections of four feet, and graduated in
feet and tenths. Complete in two cases, ...... $135.OO
Price of Current Meter No. VI, in all respects similar to that above,
but in addition to the ordinary registering apparatus
this instrument is
provided with an electric register, one battery and copper wire, as
shown in the smaller cuts on page 232. Complete in four cases, . . $195.OO
j- For further information on this Current Meter, read " Description of some experiments on the Flow
of Water, made during the Construction of Works for Conveying the Water of Sudbury River to Boston," by
. Stearns (Transactions of the Society of Civil Engineers, Jan.-March, 1883). Also, " On
, together with a Reason why the Maximum Velocity of Water Flowing in Open Channels
is Below the Surface," by F. P. Stearns; a paper read at the Annual Convention of the American Society or