DESCRIPTION OFTHE FIRTH OF FORTH. 1C5 



deep clay ; it then takes its course through a country con- 

 taining extensive beds of coal, limestone, and ironstone, so 

 that, under the lowest part of the river and the highest ba- 

 sin of the Firth, coal is dug on both sides from beneath the 

 channel. 



Thick beds of alluvial clay and copious depositions of 

 sand are found on both sides of the Firth, wherever the so- 

 lid rock does not appear. Between Musselburgh and Guil- 

 len Point, numerous patches of turfy beach, over which the 

 tide rises, are met with. The Firth appears, on account of 

 the large extensive sand-beds, and the immense quantity of 

 algae which it contains, to be favourable for the deposition 

 of the spawn of fishes. How far the Firth is fitted to be a 

 receptacle for fishes, by the kinds of food favourable to their 

 increase which it supplies, is a question that can be but im- 

 perfectly answered at present. Molluscous animals, which 

 certainly constitute the chief food of fishes, next at least 

 to their. own tribe, abound in the Firth ; but, as yet, little 

 is known as to the comparative favour in which the several 

 species of these are held among fishes, nor have we any 

 means of ascertaining the relative proportions in which the 

 different molluscous animals found in it abound. 



As might be anticipated, from the extent and irregulari- 

 ties of this estuary, the tide derived from the German Ocean 

 exhibits some anomalies. The tide flows to a mile from 

 Stirling Bridge, a distance of near eighty miles from the 

 ocean in a straight line. It is there interrupted by a rock 

 which crosses the river, and at stream tides the rise on that 

 rock is five feet. The regular flow and ebb of the tide is 

 twice in twenty-four hours, but both run about two hours 

 longer in the middle of the channel than along the shore. 



