Manchestey Mefiioirs, Vol. Iv. (1911), No. IIJ. 



XIII. The Manner of Motion of Water Flowing in a 

 Curved Path. 



By Prof. A. H. GiBSON, D.Sc 



i'luz'crsi/v College, Dundee. 

 Received fa)iitary I jlh. igii. Read February jtli, igii. 



In announcing the results of his classical experiments 

 on " The Two Manners of Motion of Water," before the 

 Royal Institution of Great Britain,* Osborne Reynolds 

 instances " curvature with the velocity greatest on the 

 outside of the curve " as one of the circumstances con- 

 ducive to direct, steady, or stream_-line motion in a stream 

 or jet of water ; and " curvature with the velocity greatest 

 on the inside of the curve " as conducing to sinuous motion 

 or eddy formation. f The experiment on which this con- 

 clusion was based was carried out b}' means of a cylindrical 

 vessel filled with water. This was allowed to come to 

 rest, after which a colour band of aniline dye was intro- 

 duced diametrically across the vessel, and the latter was 

 rotated slowly on its axis. To quote its author : " At 

 first, only the walls of the cylinder move, but the colour 

 band shows that the water gradually takes up the motion, 

 the streak being wound off at the ends into a spiral 

 thread, but otherwise remaining still. When the spirals 

 meet in the middle the whole water is in motion, but the 

 motion is greatest at the outside, and is therefore stable. 

 The vessel is stopped and gradually stops the water, 

 beginning at the outside. If the motion remained steady 



* Proc. Roy. Institittion of Great Britain, 1S84. Also " Scientific Papers," 

 vol. 2, p. 153. 

 t " Scientific Papers," vol. 2, p. 157. 

 May 4ili, igii. 



