DESCRIPTION OF THE FIRTH OF FORTH. 163 



coming narrower, through a course of nine or ten miles to 

 Queensferry, where it is about two miles across. Here it ex- 

 pands again in a beautiful basin, varying in width from 

 three to four miles, through an extent of tliirteen or four- 

 teen miles ; above this it assumes more of the character of 

 a river, and here, therefore, the estuary may be said to ter- 

 minate. 



The Islands of the Firth are important in its physical geo- 

 graphy, as exerting an important influence on its currents, 

 and thereby on the depositions from the water at the bottom, 

 and on its encroachments on its banks. The Bass, distin- 

 guished as the abode of the Gannet {Susa Bassaiid) ; and the 

 May, on which a light-house is situated, are the most conspi- 

 cuous near its junction with the ocean. Higher up, Inchkeith 

 occupies the middle space near the upper contraction of its 

 greatest basin, and determines, by its influence on the tide, 

 the ba^nks, channels, and bays, through an extent of several 

 miles. Between this island and (Queensferry, Cramond 

 Island, Inch Mickery, and Inchcolme, intersect the Firth 

 nearly in a line across, being at the distance of three or four 

 miles from Queensferry. Inchgarvey, the highest island that 

 deserves notice, occupies the middle of the contraction be- 

 tween North and South Queensferry. 



The Depth of the Forth, below the Isle of May, is up- 

 wards of thirty fathoms, declining to fourteen or fifteen 

 fathoms, as the northern or southern border is approached. 

 In the first contraction, between Elie point and Yellow 

 Craig, the greatest depth is about twenty-eight fathoms ; 

 from which, in the middle of the channel up to Inchkeith, 



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