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Second, That the whole tidal phenomena of the navigation to be 

 improved ought to be ascertained, in order that the engineer may be 

 enabled to discover in what part of the river the most prejudicial 

 retardations of the tidal wave, and obstructions of the current, take 

 place. 



Third, That, in tracing these retardations to the proper cause, 

 and suggesting means for their removal, works should be adopted 

 which do not injuriously abstract tidal water from the sea channels. 



Fourth, That the works best suited for attaining the desired end 

 consist chiefly in lowering the bed of the river, and removing all 

 natural or artificial obstructions, and in erecting low rubble walls 

 for the direction of the cun-ents. 



Fifth, That although general views of the nature of these opera- 

 tions may be given, the precise details of such works as shall bo 

 best suited to particular localities can, in the present state of our 

 information, be determined only by Engineering experience. And, 



Lastly, That, by the execution of works designed in accordance 

 with these general views, very beneficial results have been, and 

 may be, produced, for a comparatively small expenditure. 



2. On the Solvent Action of Drainage Water on Soils. By 

 John Wilson, Esq., F.G.S. Communicated by Dr Gre- 

 gory. 



The author,, being resident for a time in East Lothian, in order 

 to study the system of agriculture, it occurred to him that the very 

 extensive and complete drainage must materially atfect the soil by 

 removing large quantities of its soluble ingredients. 



He was disappointed, owing to an accident, in examining, quanti- 

 tatively, the water which had been first collected for the purpose ; 

 but on examining, qualitatively, some that was collected after the 

 drain had been running very copiously for 36 hours, he found it to 

 contain 18.4 grains of soluble matter per gallon. This was chiefly 

 the usual salts of lime and organic matter. 



He examined the surface and subsoils of the field, and found 

 them to contain, besides silica and alumina, iron, lime, and traces of 

 magnesia, with organic matter. The iron in the surface sail was in 

 the state of protoxide, but in the subsoil it was found peroxidised. 



The aiuthor concludes that the drainage water carries ofi" a very 

 large quantity of the soluble matter of the soil, which he calculates 

 as possibly amounting to 775 lbs. per acre in the year, a quantity 



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