240 PROCEEDINGS OF SECTION A. 
The curves or templates are each cut to represent a tidal com- 
ponent, according to its wave length or speed. They are on the 
scale of 1 inch to the mean solar hour (15°) and 1 inch to the 
foot in amplitude, and are true sine curves. The wave length of 
each component bears the same ratio to the solar tide, 82; as its 
angular speed does to 15°. 
The rods or plungers have each a pulley on the upper end, and 
a hard smooth point on the other. They are placed in the slots in 
the beam already mentioned, the lower end of each resting on a 
component curve ; and we have already seen there is a fixed pulley 
in the beam between each rod. A fine flexible wire is passed under 
each pulley in the beam, and over each one on the rods, through 
another in the recorder, and back through a larger fixed pulley at 
the back end of the beam, then the two ends are joined, thus 
forming and endless wire. 
The larger pulley just mentioned is fixed to a plate, which is 
movable backwards and forwards, for adjusting the index to the 
mean level of the sea. The pulley is attached to the plate by a 
fine screw, by which means a compensation is effected for the 
annual and semi-annual tides, the amplitudes of which are treated 
as constants for fourteen days, and graduations are made on the 
plate for that purpose. 
The machine is designed for twenty-three components, although 
only sixteen have been used, the amplitude of the others being so 
small that they may be neglected without any material error. 
Each template or curve is fixed in the carrier at the proper 
place according to its phase, that is, the first high water of each 
component tide is placed a certain distance from the epoch or 
starting point, determined by the previous harmonic analysis. 
The handle being turned, the carrier, verticle slide, and clock are 
set in motion, and the curves passing underneath the rods give 
them a vertical harmonic motion, which is communicated to the 
index by means of the endless wire. The pointer will then show 
the height of tide at the time indicated by the clock, and the 
curve will be traced on the paper attached to the vertical slide. 
Tt will thus be seen that the machine continuously sums the 
series and traces the curve. 
The chief feature of this machine is that all the curves move 
together at the same rate; the differences in speed being obtained 
by the difference in the wave-length of the curves. After the 
curves are once set, the working of the machine is very simple, 
all that is required being to turn the handle and watch the 
pointer ; when it stops rising it is high water, the time and height 
can be read off and recorded at once. The same thing applies to 
low water. If, as may be the case at neaps or “dodging” tide, 
the pointer does not move much either up or down, and the time 
