KiLROE — The Shannon : its Course and Geological History. 75 



Professor Hull, m.a., ll.d., f.e.s., adopted this hypothesis, 

 and points out, in his "Physical Geology of Ireland,"^ that the 

 valleys through which the Moy, Owenwee, Erne, and other rivers 

 flow outward from the central plain, may be similarly accounted for. 



Some interesting items of information are to he gleaned from the 

 Parliamentary Papers on the subject of the ^Shannon Navigation. 

 The minutes of evidence by Col. John Eox Burgoyne (vol. xvii, 1834, 

 p. 4) deal with the regimen of the river from Lough Allen to 

 Limerick, and set forth the facilities for commercial traffic along the 

 three sections, viz. : The Upper Shannon, comprising the stretch from 

 Lough Allen to Lough Eee ; the Middle Shannon, from Lough Eee 

 to Lough Dcrg ; and the Lower Shannon, from Killaloe to Limerick. 



Still more interesting information is afforded by the Admiralty 

 Charts, which set forth the soundings of the expansions of the 

 Shannon in considerable detail. 



Facilities were in existence prior to 1834 for passing the shallows 

 at Athlone and Killaloe by means of canals and locks ; powers for- 

 merly possessed by the Board of Inland IS'avigation had already been 

 transferred to the Board of Works (Ireland), which is in possession 

 of levels of the river-bed at several points ; and these data have been 

 kindly placed at my disposal by the officers of the Board of Works, 

 without which any scientific discussion of the physiography would 

 necessarily be incomplete. 



The Shannon takes its rise in the townland of Derrylahan, in 

 Cavan — issuing from a deep, roundish hole or pond, which is the 

 outlet of an underground stream. The lakelet is locally known as 

 Legnashinna, 345 feet above datum, upon a limestone col, which 

 forms the waterparting between the basins of the Shannon and the 

 Erne.^ The limestone is very cavernous, traversed by several under- 

 ground streams ; and the water which issues from Legnashinna has 

 been traced to another lakelet, about \^ mile north-eastward, Lough 

 Garvah (512 feet above datum), which forms a natural reservoir for 

 streams visible and concealed. Tracing these rills still higher, the 

 actual watershed is reached, which, in this locality, is 600 feet 

 above datum. 



^ Sixth edition, 1894, p. 363. 



2 According to Joyce (" Irish Names of Places," pp. 75, 272, third ed., 1871), 

 Shannon was called Senos on Mercator's edition of Ptolemy's Map, 1605. 

 'Legnashinna' may be a later Irish form of 'Shannon,' joined with 'leg,' 'a 

 hollow.' Shannon, near Lilford in Donegal, was probably Shandon, after ' Sean 

 Dun,' 'Old fort.' 



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