312 



On the Fall of Bivers. 



Macnean and Lough Allen, and is 345 feet above the sea. 

 After a course of IIG miles, it enters Lough Allen, up to 

 which it is rendered navigable, owing to the little descent 

 from that place. The distance to which it is navigable is 

 213-8 miles from its mouth ; and in this respect it is superior' 

 to all other British rivers — the navigation of the Severn ex- 

 tending only 192, and that of the Thames 193 miles from 

 their mouths. From the head of Lough Allen to the foot of 

 Lough Derg, a distance of 131*8 miles, it descends only 505 

 feet, or 4j inches per mile. After leaving Lough Derg, the 

 inclination of its course changes considerably, and gradually 

 increases, till it reaches a fall of nearly 17 feet per mile be- 

 tweon the town of Castle Connel and Castle Troy, a distance 

 of 33 miles. It is in this portion where the mighty Shannon, 

 40 feet deep and 300 yards wide, forms the magnificent 

 Rapids of Doonas. 



The Fall of the Shannon. 



