Wood’s Portable Self-Registering Tide-Gauge. 1c 
X the axis of the wheel W W is to be proportioned so that 
its diameter shall be smaller than the diameter of the wheel, 
in the same ratio in which it is desired that the scale of the 
register shall be smaller than the rise and fall of the tide. 
RR and,s ¢ are tworollers; the under one 7 7 is furnished 
with the paper rolled round it. A stripe from the side of a 
sheet of drawing paper, 40 inches long and 93 inches broad, 
is sufficient for this purpose. The upper roller R R has one 
end of the paper fixed on it, so as, by revolving, to roll the 
paper gradually on itself, the roller 7 x being steadied by the 
presence of a small spring. 
SS is a large copper ratchet wheel, detained by the copper 
pall p p, the under surface of which is serrated in a similar 
way to the wheel with numerous small teeth, and is pressed 
to the wheel by a small spring; thus the roller R R is de- 
tained in any position to which it has been moved. 
Motion is given to the roller once in each tide about half 
ebb. This is effected in the following manner :—One tooth 
of the ratchet wheel is moved each tide by the ratchet ¢ ¢ at- 
tached to a vertical bar moving up and down on two guide 
pins. This bar is loaded to drop with its own weight, and a 
loaded lever L L raises it once each tide. 
The lever L L receives motion from the axle of W W once 
in each tide, as follows :—The chain C C winds upon the axle 
X as the tide rises, and is of such a length as to be quite 
slack at low water,and to become tight at half tide: the lever 
is then raised, and the ratchet bar falls about one tooth and 
a-half, so as to be quite free of the wheel. The lever con- 
tinues to rise till high water, and in falling, at about half ebb, 
once more raises the ratchet bar, and by it turns the roller 
RR through one tooth, a stop preventing any further motion. 
As the tide ebbs further, the lever chain becomes slack, and 
does not again come into operation until the middle of the 
following tide. 
Behind the travelling bar T T, which carries the Register 
pencil, is a fixed bar F F, carrying another pencil G, adjust- 
able in position so as to describe, when once adjusted, a datum 
line on the paper, to represent any fixed height that may 
be referred to as a standard for the height of the tides, and 
