Two harmonic analyzers are shown on the Fourier analysis page. In addition, besides the picture on the Tides base page this page is keyed to, machines are mentioned in connection with Beauchamp Tower's suggestion.
Kelvin's Tide Predicter
Click for larger image.
This machine was exhibited at the South Kensington Museum,
where it currently resides, in 1876.
It is designed to sum the
M2, S2, N2, K1, O1, K2, L2, P1, M4 and MS4
constituents, in that order reading from the left. (See
Kelvin, p. 289). ``The
machine may be turned so rapidly as to run off a year's
tides for any port in about four hours.''
The U. S. Coast and Geodetic
Survey Tide Predicting Machine No. 1
The U. S. Coast and Geodetic
Survey Tide Predicting Machine No. 2
This machine, built by R. A. Harris and E. G. Fischer,
was completed in 1910. According to
Schureman it is about 11 feet long, 2 feet wide, 6 feet high,
and weighs approximately 2,500 pounds. It is designed to sum 37
constituents. This machine was used from 1912 until 1965 to generate tide
tables for U. S. ports. It sits at present in the lobby of the
NOAA in Silver Spring, MD.
There are 2 complete sets of pulleys, one on each side
of the machine, running in tandem. Those on the left side
sum the heights of the constituents. Those on the right,
or ``time'' side, sum their derivatives, so a high or low
tide (a local maximum or minimum) is registered by the index
on the time chain passing zero (see below).
This side view shows some of the pulleys and the cams designed
to convert rotational motion of the gears into vertical
motion of the pulleys. The total length of the chain linking
the pulleys on this side is 27.6 feet. Schureman's
book gives complete instructions for how to set and run this machine.
For example, on p. 142:
``If the predicted high and low waters for the year are desired,
the operating crank is turned forward until the machine is automatically
stopped by the brake at a high or low water. To avoid the strain on the
machine due to sudden stops, the operator should watch the small index
on the time chain, and as this approaches the fixed index in the center
of the opening on the face of the machine, turn the crank more slowly
until the machine is stopped as the indexes come in contact with each other.
The time and height may then be read directly from the dials on the
face of the machine. The movement of the height pointer before the
stopping of the machine and also the tide curve will clearly
indicate whether the tide is a high or low water. After the tide
has been recorded an inward pressure on the crank handle will
release the brake and the machine can be turned forward to
the next tide, the process being repeated intil all the tides of
the year have been predicted and recorded.''
The crank was replaced by an electric motor for the last 5
years of the machine's operation (1960-65).
This machine, built by William Ferrel in 1885, was used
for prediction through 1911. It summed 19 constituents. This
is presumably the machine on display in the Smithsonian.
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