1879.] Mr. E. Roberts. On a new Tide-Predicter. 



201 



The recording barrel is fitted with, brass pins at equidistant inter- 

 vals to form the time indications on the paper by perforation. An 

 index for setting is fitted behind the machine at the top of the re- 

 cording barrel. 



The paper, which is continuous and supplied from a reel, passes 

 round two grooved rollers at the back of the main barrel, and is held 

 in position whilst the pins enter the paper, and after receiving the 

 curves is wound round the haul-off dram. The haul-off drum rests on 

 toothed driving-wheels, and by friction turns and slips to accom- 

 modate itself at a proper tension to receive the recorded paper. 

 Motion is given to the whole system of wheel work through the 

 horizontal centre main shaft from a system of clockwork driving- 

 gear at the bottom of the machine, the whole being driven by a 

 weight calculated at about 4 cwt., and controlled by a fan. A 

 warning bell sounds when the weight is nearly run down. The length 

 of the barrel round which the cord is wound is sufficient to give 

 15,000 turns of the main shaft. This corresponds to about 3 months' 

 run of curves, and will occupy about 1 hour to run off. A year's 

 tide-curves for any port will thus occupy about 4 hours. 



The setting of the machine for the prediction of the tide-curves of 

 any part for which the tide-components are known, is as follows : — 

 The dials are first turned so that the epoch or time of maximum is 

 exactly under or above the highest or lowest point according as the 

 component is situated on the upper or lower row of components. 

 The cranks are set vertically (the slotted cone of the wheel on the 

 axis having been first released) arid the guide-pin thrown out to its 

 proper range to represent the half-amplitude of the component. The 

 proper positions of the hands having been previously determined by 

 calculation for the time of starting, the hands are set and the slotted 

 cones tightened up. The recording barrel is then set to the time and 

 the wheelwork set in motion. The complete setting occupies only a 

 few minutes. 



The large dial in the centre is for showing the progress of the 

 record, which can be marked occasionally to facilitate the entry of the 

 dates on the record after its removal from the machine. A few 

 supplementary pins are inserted in the barrel for the better distinction 

 of the hours. Two speeds of travel can be given to the paper, viz., 

 1 inch and |-inch per hour. A fixed rod near the recording pen 

 carries ruling pens for the tracing of base lines, such as dock sills, 

 river bars, or mean tide-levels, or if desired can rule the paper 

 throughout its entire depth to represent feet, metres, &c. 



To Sir William Thomson the author's thanks are due for the im- 

 proved parallel slide and other details, and also to Mr. Lege (the maker 

 of the instrument) for the design of the wheel-gearing. 



