228 Roi/al Society. 



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, « Un 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 difl'erent 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 

 full, the author concludes, that they are in the ratio of the areas of 

 the orifices, independently of their shape ; and nearly as the square 

 roots of the heights. In pipes bent at various angles the retarda- 

 tion occasioned by the flexure was not in proportion to their num- 

 ber. 



A paper was read, " On the Sources and Nature of the Powers on 

 which the Circulation of the Blood depends." By A. P. Wilson 

 Philip, M.D. F.R.S. L. & Ed, 



In the first part of this paper the author discusses the opinions 

 which ascribe the powers that maintain the circulation in the veins 

 to the elasticity of the heart, the resilience of the lungs, and the 

 dilatation of the thoracic cavity in the act of inspiration. He shows 

 experimentally that the circulation continues unimpaired when all 

 those causes have ceased to operate ; and that the very structure of 

 the veins, the coats of which are so pliable as to collapse by their 

 own weight, when empty, renders it impossible that the motion of 



the 



