A GRAPHICAL REGISTRER OF TIDES AND WINDS. 
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raises, in its turn, a hammer, whose fall strikes an impression on the paper once 
in every hour, so that the spaces passed through are measured as they occur, 
and leave no error that might otherwise arise from the expansion or contrac- 
tion of the materials. It is obvious that when the paper has been taken off the 
machine, vertical lines must be ruled across the paper through the hourly 
points made by the hammer, and any of them may be subdivided into less 
measures of time if required. Immediately over the axis of the cylinder, and 
parallel with it, is a rack, which carries a pencil, and is acted upon by a pinion, 
which receives its motion from a float resting upon the water ; so that as the 
tide rises and falls, the pencil moves backwards and forwards at a proportional 
rate, although through diminished space, and thus by the combined motions 
of the clock and the tide, a line is produced on the paper which represents 
both. 
The impression hourly struck by the hammer is the figure of an arrow with 
a cross in the centre, the point of intersection being that through which the 
hour lines are drawn. The figure is cut on the end of an upright punch, which 
is connected with a weather-cock on the top of the house in which the machine 
is placed, and hence the direction of the arrow will always correspond with 
that of the wind, which becomes hourly registered. 
The marking point for the tidal line is of steel, which makes such an im- 
pression on the paper as will be easily traced with a camel’s hair pencil when 
the paper is removed, as will also the impression made by the wind arrow. A 
pencil, usually called the metallic pencil, may be employed for the original 
line if preferred. 
The float which rests on the water is a hollow plate-iron vessel, suspended 
by a chain which passes twice round a light cast-iron barrel, and then de- 
scends, having a counter weight attached to it. The chain is of such a length, 
that both ends of it are always resting on the ground, so that the weight of 
chain on each side of the barrel is always equal. 
The float is placed in a well communicating with the river, and to prevent 
that undulating motion which would be produced by the motion of the surface 
of the river during high winds, the water is received into the well through a 
fine wire gauze. 
The motion is communicated from the float in the well to the machine in 
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