152 History of Inland Transport 



to a height of 40 ft.; while " Chambers' Encyclopaedia " gives 

 47 ft. above low-water mark as the height to which the tide 

 has been known to rise in the same river at Chepstow. 



Of the floods in the Yorkshire Ouse Rodolph De Salis 

 says in " Bradshaw's Canals and Navigable Rivers of Eng- 

 land" (1904): "The non-tidal portion of the river above 

 Naburn Locks is liable to floods, which at York often reach 

 a height of 12 ft., and have been known to attain a height 

 of 16 ft. 6 in. above summer level." 



The liability of English rivers to a shortage of water would 

 seem to be as great as their liability to excess of it. In 

 Archdeacon Plymley's " General View of the Agriculture 

 of Shropshire " (1803) there is published a table, compiled 

 by Telford, giving the heights reached by the Severn be- 

 tween 1789 and 1800. It shows that, as against some very 

 serious floods and inundations, the river often, during the 

 dates mentioned, ran for considerable periods with a stream 

 of no more than sixteen inches of water ; that it frequently 

 had less than a foot of water ; and that in times of extreme 

 drought the depth of water had been reduced to nine inches. 

 In 1796, the period during which barges could be navigated 

 even down-stream with a paying load did not exceed two 

 months, and " this interruption," it is stated, " was severely 

 felt by the coal-masters, the manufacturers of iron, and the 

 county in general." 



The navigation of the Trent is declared in " Rees' Cyclo- 

 paedia " to be "of vast importance to the country " ; yet 

 the authority of John Smeaton, who had examined the river 

 in 1761, is given for the statement that in several places the 

 ordinary depth of water did not exceed eight inches. In the 

 upper part of the river there were, in 1765, more than twenty 

 shallows over which boats could not pass in dry weather 

 without flushes of water. 



The inadequate depth of water may be due, not alone to 

 drought, but to the formation of shoals or shallows owing to 

 the rapid fall of the river, its excessive width, or the amount 

 of sediment brought down from the hill-sides or washed 

 from the bed over which it flows. Alternatively, much silting- 

 up may be caused by the sand brought into the river by in- 

 coming tides, and not always washed out again by out-going 

 tides. 



