TRANSACTIONS OF SECTION G. QQ^> 



The chalk is turned into a cream or shid>?e, which can be pumped out and 

 delivered at the mouth of the tunnel or elsewhere. 



4. Improved Continental Communication. By James Abernethy, C.-B. 



The author proposed to establish a service of large steamers between Calais and 

 Dover, on wbinli entire trains could be conveyed across the Channel. The steamer 

 would be 470 feet in length ; GO feet beam ;' 0,000 tons; with engines of 12,000 

 indicated horse-power; the draft loaded to 12 feet; estimated speed, 23 miles. It 

 is thought that vessels of this size would not feel any movement iu the Cliannel. 

 The cost for three steam-vessels, and the necessary works at Dover and Calais, was 

 estimated at a million and a half. 



5. On Unsteady Motion in Open Channels} 

 By Major Allan Cunningham, B.E. 



The motion of water in open channels is essentially an unsteady motion tvith 

 interlacing stream-lines ; the hypothesis of steady parallel motion is at variance with 

 nature. 



Single velocity measurements are of little practical use, being only accidental 

 values; the average of a large number is pretty constant, so that the average 

 velocities should always be sought. The time needed to obtain these involves a 

 chance of change of the external conditions. 



In practical hydraulics the forward velocity is the only velocity considered or 

 required. Floats measure this directly ; no other instruments yield this quantity 

 readily iu large streams. 



These principles are of great importance, and sliow that hydraulic experiments 

 must always be tedious and expensive. 



6. Convexity of Surface of Streams.^ By Major Allan Cdnningham, B.E. 



The figure of the transverse section of the free surface of a stream, usually 

 supposed to be convex, is here considered. The evidence is shown to be very 

 small. Some new special experiments are cited. The conclusion is that the surface 

 is probably level across. 



7. Depression of Maximum Velocity} By Major Allan Cunningham, B.E. 



The line of maximum velocity in an open channel is usually below the surface. 

 The cause of the depression is obscure. The wind and disturbances from the 

 banks and bed are usually supposed to be the causes. The wind is probably too 

 inconstant. The disturbances from the banks and bed seem an inadequate ex- 

 planation. The general depression of the maximum %elocity on all verticals at all 

 parts of a channel indicates some resistance from above. The motion in open 

 channels and in pipes flowing full shows some similarity, with differences in detail 

 fairly accounted for by supposing the air to be an ever-present drag or source of 

 resistance to forward surface-flow less efficient than the banks or bed. If this be 

 admitted, the hydraulic term, ' wet border/ must be modified so as to include all 

 jyarts of the wet border, eacli with its own specific resistance. 



SA TURD A Y, A UG UST 26. 

 The Section did not meet. 



' See Itoorlicc llydrauUc Experimcntsi, by Major Allan Cunningham, R.E. 

 Roorkee, 1881. Vol. i. ch. vi. 



"^ Ibid. vol. i. ch. \-iii. ^ Ibid. vol. i. ch. xii. 



