384 On Flux and Reflux of Water in Open Channels. 



ence due to the landward surface declivity of the water in the 

 estuary. 



Exactly a like explanation, mutatis mutandis, is applicable 

 to the case of reversal of the flow from having been landward 

 to its becoming seaward. The channel-face lamina makes its 

 reversal of flow, just as in the other case, earlier than does the 

 main body of the water, and for like reason. 



It may now further be noticed that precisely corresponding 

 phenomena would present themselves in the flux and reflux of 

 water in a pipe ; if, for instance, the pipe were connecting 

 two cisterns, and a plunger were kept oscillating upwards and 

 downwards in one of them so as to cause the alternating flow 

 through the pipe. The phenomena might be very interest- 

 ingly manifested in an open trough connecting two cisterns, 

 arrangements being made, by a plunger or otherwise, for 

 causing flux and reflux along the trough, and the motions of 

 the water being indicated by small visible particles in suspen- 

 sion in the water, or by the dropping in of granules of aniline 

 dye. 



It may now be worthy of remark that the hydraulic prin- 

 ciple brought into notice in the present paper, in respect to 

 Flux and Eeflux along Channels, is closely allied to, and is 

 in some respects identical with, the leading principle set forth 

 in previous papers by myself on the Flow of Water round 

 Bends in Rivers, &c. In that case the frictionally resisted 

 and retarded lamina in contiguity with the channel-face, or 

 bed, flows transversely (or rather obliquely) across the channel 

 towards the inner bank of the bend, impelled inwards by gra- 

 vitational propulsive influence (that is, downhill as it were), 

 while the main body of the stream, flowing quicker in the 

 bend, exerts centrifugal force outwards, or tends inertially 

 out towards the outer bank. The papers here referred to on 

 Flow of Water round Bends in Rivers, &c. are to be found in 

 the ' Proceedings of the Royal Society ' for May 1876 ; in the 

 British Association Report for the Glasgow Meeting, 1876, 

 Section A, page 31 of Transactions of the Sections ; in the 

 < Proceedings of the Royal Society, 5 1877, No. 182, page 356 ; 

 and in the l Proceedings of the Institution of Mechanical 

 Engineers,' August 1879, p. 456. Also some other important 

 cases in which like principles of fluid motion come into play 

 (in Whirlwinds &c.) are adduced in a paper by myself in 

 the British Association Report for the Montreal Meeting, 1884, 

 Section A, page 641. 



The University, Glasgow, 

 September 5, 1888. 



