63 



the time and height of high water, not only at different periods of 

 the moon's age, but also for the different months of the year, for 

 every minute of the moon's parallax, and for every three degrees of 

 her declination. The tables themselves were registered by LMr. 

 Dessiou of the Admiralty : but the arrangement of the tables and 

 the methods employed are due to the author. The tides in the river 

 Thames are extremely regular; and as the rise is considerable, the 

 observations on them are easily made. Those at the London Docks 

 present an uninterrupted series from the opening of the Docks in 

 1804 to the present time: which is more extensive than any extant, 

 with the exception only of that made at Brest by order of the French 

 Government. Some observations are also given of the tides made 

 during one year at the East India Docks, under the superintendence 

 of Captain Eastfield, and which were undertaken at the suggestion 

 of the author, and made with extreme care. 



The author gives an account of the mode by which the several 

 tables were constructed; and enters at length into the various ma- 

 thematical considerations which the subject involves. 



The author was enabled, by the kindness of the Chairman and 

 Directors of the London Dock Company, to present to the Society 

 the books containing the complete series of original observations on 

 the tides referred to in this paper. 



A paper was read, "On the Friction of Fluids." By George 

 Rennie, Esq., V.P.R.S. 



The object of the author in this paper is to trace the relation sub- 

 sisting between the different quantities of water discharged by 

 orifices and tubes, and the retardations arising from the friction of 

 the fluid. The results of the experiments hitherto made with a 

 view of ascertaining the effects of the friction attending the mutual 

 motion of solids and fluids, are exceedingly discordant, and there- 

 fore undeserving of confidence. Whether, for example, the retarda- 

 tion from friction be proportional to the surfaces, or to the velo- 

 cities, are points by no means satisfactorily determined. 



The experiments of the author were designed to measure the re- 

 tardations experienced by solids moving in fluids at rest; and of 

 fluids moving over solids. For this purpose, he employed a cylinder 

 of wood^ about eleven inches in diameter and two feet in length, 

 traversed by an iron axle, upon the upper part of which a small 

 pulley was fixed. A fine flexible silken cord was wound round the 

 pulley, at one end, and had a weight attached to the other end. A 

 frame was provided, allowing the apparatus to slide up and down; 

 and the cylinder to be immersed at various depths into the river 

 Thames. When the velocities were small, the retardation was found 

 to be nearly as the surface : but with great velocities it appears to 

 have but little relation to the extent of the surface immersed. The 

 resistances of iron discs and wooden globes revolving in water were 

 found to be as the squares of the velocities. 



From the experiments made on the quantities of water discharged 

 by orifices of different shapes and sizes from vessels kept constantly 



