508 Mr. L. F. Vernon-Harcourt. . 



principles for guidance in training rivers through estuaries. The 

 estuary of the Seine is in some respects peculiarly well adapted for 

 such an investigation, for old chai-ts exhibit the state of the river 

 before the training works were commenced, arid recent charts indicate 

 the changes which the training walls have produced, whilst the 

 various designs for the completion of the works, proposed by ex- 

 perienced engineers, afford an interesting basis for experimental 

 inquiries into the principles of training works in estuaries. If, in the 

 first place, it should be possible to reproduce in a model the shifting 

 channels of the Seine estuary as they formerly existed, and next, after 

 inserting the training walls in the model as they now exist in the 

 estuary, the effects produced by these works could be reproduced on a 

 small scale, it appeared reasonable to assume that the introduction, 

 successively, in the model of the various lines proposed for the exten- 

 sion of the training walls would produce results in the model fairly 

 resembling the effects which the works, if carried out, would actually 

 produce. 



When the third Manchester Ship Canal Bill was being considered 

 by Parliament in 1885, Professor Osborne Reynolds constructed a 

 working model of the portion of the Mersey estuary above Liverpool 

 on behalf of the promoters of the canal, with the object of showing 

 that no changes would be produced in the main channels of the estuary 

 by the canal works which had been designed to modify very slightly 

 the line of the Cheshire shore above Eastham. This model was, 1 

 believe, the first experimental investigation on an estuary by artifi- 

 cially producing the tidal action of flood and ebb on a small scale ; 

 and Professor Reynolds' experiment showed that a remarkably close 

 resemblance to the main tidal channels in the inner estuary could be 

 produced on a small scale. 



As the Mersey model did not extend into Liverpool Bay, the tidal 

 action produced was very definitely directed along the confined 

 channel representing the " Narrows " between Liverpool and Birken- 

 head ; and this tidal flow was not perceptibly influenced by the rela- 

 tively very small fresh-water discharge. In the Seine, however, there 

 is no narrow inlet channel to adjust exactly the set of the flood tide into 

 the estuary ; and the large fresh- water discharge of the Seine, with a 

 basin about eighteen times larger than the Mersey basin, forms rn 

 important factor in the result. The tide in a model of the Seine has 

 to be produced in the open bay outside the estuary at a suitable angle 

 which had to be determined ; and it was essential for the success of 

 the Seine experiments that accretion should be produced in the model 

 of the Seine estuary under certain circumstances, which was a con- 

 dition which did not enter into the Mersey problem. Accordingly, 

 the very interesting and valuable results obtained by Professor 

 Reynolds, in his model of the Mersey, could afford no assurance that 



