72 Wood's Portable Self-Registering Tide-Gauge. 
In practical engineering, the improvement of rivers and 
harbours, and, in marine surveying, the possession of such 
an instrument is of no less value than in abstract science. 
I have satisfied myself that the machine invented by Mr 
Wood possesses, or is capable of achieving, all that is desired 
on this head. I therefore think it my duty, through this So- 
ciety, to make known the merits and construction of a useful 
machine, which has its origin in the pure love of scientific 
truth which animates the mind of its accomplished inventor. 
Mr Wood’s Self-Registering Tide-Gauge has been at work 
in Port-Glasgow for about two years. It has no clock-work, 
nor the barrel D. It registers the height of high and low 
water for four months without requiring any attention what- 
ever. At the end of that time, a new sheet of paper should 
be supplied to the machine, the old one removed, and the 
pencils repaired. Airey’s HH, or H HH, will last this 
period in good order. 
On removing the paper, the observer finds a diagram of 
the tides, on which are simply, and at once, presented the 
curves of geometrical inequality and the diurnal inequality, 
&e. 
A specimen of the work of the machine is sent herewith. 
It contains about three months’ observations. 
The whole machine is portable and light, and may easily be 
transported. A box less than 18 inches square in the bottom, 
and about 12 inches deep, contains it. 
A (Plate III.) is the wooden float, about 2 lb. weight, sus- 
pended on one side of the wheel WW; and on the other 
side is the counterpoise weight B, of 1 lb., givmg a moving 
power of 1 lb. each way. 
TT is a horizontal travelling bar, carrying the register 
pencils H and O. This bar is made to traverse with the rise 
and fall of the float, by means of two chains C CC, one end 
of these chains being attached to the travelling bar, and the 
other end coiled round the axis X of the wheel W W, round 
which each chain has one turn and a half when the register 
pencil is in its mean position. These chains should have a 
small degree of slackness, to be afterwards allowed for on 
reckoning the ranges. 
