Royal Society. 359 



is caused, not so much by evaporation as by the direct effect of the 

 solar rays : for he remarked, that when there was a succession of 

 clouds passing over the sun, the tremor was very great at those times 

 when the sun shone ; but the moment the sun was obscured over the 

 whole space between the instrument and the object viewed, the air 

 was perfectly tranquil. 



Mar. 10. It being stated to the Meeting by the President that 

 Mr. Caldcleugh, elected that evening, was on the point of leaving 

 England for Mexico, and would consequently have no other oppor- 

 tunity during this session of attending for admission, Mr. Caldcleugh 

 was allowed to sign the Obligation in the Charter Book, and was ad- 

 mitted a Fellow of the Society. 



A Paper was read, entitled, " Description of a Graphical Register 

 of Tides and Winds." By Henry R. Palmer, Esq., Civil Engineer. 

 Communicated by J. W. Lubbock, Esq. V.P.&Treas.R.S. 



The author having long directed his attention to the effects likely 

 to be produced on the tides in the river Thames, in the port of Lon- 

 don, by the removal of London Bridge, was desirous of obtaining a 

 series of accurate observations during all the changes of the tides ; 

 and for this purpose constructed a machine, which, being acted upon 

 jointly by a time-piece and by a float resting on the water, registered 

 of itself, upon a piece of paper, both the height of the tide, and the 

 direction of the wind. 



A number of parallel and equidistant lines, representing feet in 

 height, are engraved, and printed on long sheets of paper, the ends 

 of which are joined together until a sufficient length is obtained for 

 the purpose required. This long sheet is wound upon a brass roller, 

 which is placed near the lower part of a cylinder one foot in diameter, 

 so that the paper may pass round it ; its contact being preserved by 

 a roller above, pressing upon it by its own weight. On the axis of 

 the cylinder is a toothed wheel, which is acted upon by a clock, pro- 

 ducing an equable motion in the cylinder, which is thus made to 

 complete one revolution in six hours. By means of another wheel, 

 at the expiration of every hour a hammer is raised, whose fall strikes 

 on an upright punch connected with a weather- cock on the top of the 

 building ; and the figure of an arrow being cut on the lower end of 

 this punch, an impression of the arrow is made upon the paper : as 

 the direction of the arrow always corresponds with that of the wind, 

 the direction of the latter is thus hourly registered. 



Immediately over the axis of the cylinder, and parallel with it, is 

 a rack carrying a pencil. The rack is acted upon by a pinion, which 

 receives its motion from the float on the water : so that as the tide 

 rises or falls, the pencil is moved backwards and forwards through 

 a space which bears a determinate ratio to the actual rise or fall of 

 the float : and thus, by the combined motions of the cylinder and of 

 the pencil, the one regulated by the clock and the other by the tide, 

 a line is traced on the paper, giving a representation of both. 



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, 



