328 



this law, and renders theory inapplicable ; while experiment, as the 

 author remarks, has not yet supplied the defect. 



The author devotes the first part of his paper to a consideration of 

 the experiments made by Bossut and other members of the French 

 Academy in 1776, 1778, and by the London Society for the Improve- 

 ment of Naval Architecture in 1793 and 1798. Both these sets of 

 experiments he regards as inconclusive, partly from the small size of 

 the floating body and the small velocities used, but chiefly from the 

 inadequacy of the means of measuring the actual resistance, and the 

 sources of error arising from the rigidity of the cords used, the fric- 

 tion of pulleys, and that of the line itself dragged through the water, 

 the moving power being a weight suspended and descending uni- 

 formly. 



In the experiments which form the object of this paper, all these 

 sources of error (which, in some cases, amounted to three times the 

 resistance to be measured,) were avoided by the simple contrivance 

 of estimating the strain exerted on the boat, at every instant, by a 

 spring weighing machine immediately attached to it, through which 

 the tension of the cord was of course transmitted, and which mea- 

 sured the actual tension exerted in overcoming the resistance of the 

 boat, unmixed with any of the other causes of the destruction of power. 



The apparatus employed is illustrated by drawings. The experi- 

 ments were made in the East India Import Dock, whose size and 

 depth are such as to allow no resistance arising from the sides or 

 bottom of the dock. The boat being drawn at each experiment over 

 -rVths of a mile, the time of passing over T Vth was carefully noted, 

 and the tension or resistance read off and registered every two se- 

 conds. The velocity was preserved uniform by applying the power of 

 men turning a barrel in measured time by the swing of a pendulum. 



Four sets of experiments were made on boats of 18 and 28 feet in 

 length, variously loaded, and on a Thames wherry, with velocities 

 from 2 to 5 1 miles per hour ; and the conclusion from them all is, 

 that the resistance increases in a higher ratio than as the square of 

 the velocity. 



Mr. Walker concludes this paper with a comparison between the 

 effect of moving power applied on a rail-road and on a canal, which 

 from these experiments appears to be reduced to equality at lower 

 velocities than if the resistance to the boat were as the square of the 

 velocity. 



On the Corrections in the Elements of Delambre's Solar Tables re- 

 quired by the Observations made at the Royal Observatory, Greenwich. 

 By George Biddell Airy, Esq. M.A., Fellow of Trinity College, 

 Cambridge, and Lucasian Professor of Mathematics in the University 

 of Cambridge. Communicated by John Frederick William Herschel, 

 Esq.V.P.R.S. Read December 6, 1827. [PAz7.7Va/w.l828,^.23.] 



The author was desired by the Board of Longitude to examine the 

 discordancies between the right ascensions of the sun, as observed at 



