386 



CKAIG-ELLACHIE BRIDGE. 



PART VIII. 



measure removed. Its utility was so generally felt, that 

 the demand arose for a second bridge across the river ; 

 for there was not another by which it could be crossed 

 for a distance of nearly fifty miles up Strath Spey. It 

 was a difficult stream to span by a bridge at any place, 

 in consequence of the violence with which the floods 

 descended at particular seasons. Sometimes, even in 

 summer, when not a drop of rain had fallen, the flood 

 would come down the Strath in great fury, sweeping 

 everything before it ; this remarkable phenomenon being 

 accounted for by the prevalence of a strong south-westerly 

 wind, which blew the loch waters from their beds into the 

 Strath, and thus suddenly filled the valley of the Spey. 1 

 The same phenomenon, similarly caused, is also frequently 

 observed in the neighbouring river, the Findhorn, cooped 

 up in its deep rocky bed, where the water sometimes 

 comes down in a wave six feet high, like a liquid wall, 

 sweeping everything before it. To meet such a con- 

 tingency, it was deemed necessary to provide abundant 

 waterway, and to build a bridge offering as little resist- 

 ance as possible to the passage of the Highland floods. 

 Telford accordingly designed for the passage of the river 

 at Craig-Ellachie a light cast iron arch of 150 feet span, 

 with a rise of 20 feet, the arch being composed of four 

 ribs, each consisting of two concentric arcs forming 

 panels, which are filled in with diagonal bars. The 

 roadway is 15 feet wide, and is formed of another arc of 

 greater radius, attached to which is the iron railing ; the 

 spandrels being filled by diagonal ties, forming trellis- 

 work. Mr. Robert Stephenson took objection to the two 

 dissimilar arches, as liable to subject the structure, from 

 variations of temperature, to very unequal strains. Never- 

 theless this bridge, as well as many others constructed 

 by Mr. Telford after a similar plan, has stood perfectly 



1 Sir Thomas Dick Lander has 

 vividly described the destructive cha- 

 racter of the Spey-side inundations in 



his capital book on the ' Morayshire 

 Floods.' 



