registering the Variation.i of the Tide and Wind. 313 

 tages that would result from the constant operation of a self-act- 

 ing machine, so constructed as to furnish the data required in that 

 interesting branch of science connected with the motions of the 



tide. . 



I now proceed to describe the mechanism represented m the 



accompanying drawing. 



The general principle of the machine is such, that a circular 

 dial being fixed to the axle of a clock, revolves with a uniform 

 motion otce in twenty-four hours ; a pencil is also moved verti- 

 cally up and down by the rise and fall of the tide ; which com- 

 bined motions of the dial and pencil trace a curve upon the face 

 of the dial, whereby the height of the tide, at any particular pe- 

 riod of time, may be ascertained, also the time of high and low 

 water, and the variable rate of ascent and descent. 



The direction of the wind is indicated by a circular dial fixed 

 horizontally to the vertical axis of a wind-vane. And, by means 

 of the clock, a pencil is made to move uniformly, at a given rate, 

 from the centre of the dial towards the circumferetice, so that if 

 the wind remain stationary upon any point of the compass, the 

 mark traced by the pencil will be a straight line, radiating from 

 the centre of the dial ; but if the wind be changing, the dial 

 will revolve, and the combined motions of the dial and pencil 

 will trace out a curve by which the direction of the wind at any 

 particular period of time will be indicated. 



Fig. 1 . PI. Ill- represents the general elevation of the machine. 

 It need not necessarily be formed as here represented, it being 

 merely required that the weather-vane be properly elevated to be 

 freely acted upon by all winds. 



Fig. 2. represents the interior construction of the machine. 

 A is a case inclosing a strong clock, which causes the dial-plate 

 BC, fixed to its shaft, to revolve once in twenty-four hours. D is 

 a large air-tight vessel, which, floating on the surface of the wa- 

 ter, ascends and descends agreeably to the rise and fall of the 

 tide, and thereby causes the wheel EF to revolve. G is a small 

 pinion fixed to the axle of the wheel, and working into the rack 

 HK, to which the pencil L is fixed. By this construction the 

 pencil will be moved vertically up and down agreeably to the 

 rise and fall of the tide, and as the circular dial-plate, fixed to 

 the shaft of the clock is turned round, the pencil will trace out 



