484 FOURTH REPORT 1834. 



however, the system of catch-water drains to intercept the 

 waters from the higher grounds, and then a system of shallow 

 drains to deliver tlie surface-water of the bog into the natural 

 streams : these drains will of course vary in number and di- 

 mensions, but in no case ought they to exceed six feet in depth. 

 Mr. Griffith agrees with the principles of irrigation laid down 

 by Mr. Nimmo. 



From the results of the reports it appears that the number of 

 English acres of bog which have been surveyed in the twenty- 

 five districts amounts to 1,013,358 



And that there remain upon the three mountain 



districts of Wicklow, Erris, and Connemara . . 387,090 

 Exclusive of peat soil, which forms the general cover- 

 ing of these mountains 355,000 



besides other lands, not examined ; from all of which it is in- 

 ferred that the extent of peat soil in Ireland exceeds 2,830,000 

 English acres, — whereof 1,576,000 are flat red bog, — which 

 might be converted to the general purposes of agriculture. 



As regards the Shannon river, which forms the most import- 

 ant feature in the internal navigation in Ireland, various 

 examinations and surveys have been made, from the year 1715 

 down to the present time : the most detailed reports have 

 been made by Mr. Rennie, Mr. Grantham, Captain Mudge, 

 Mr. Rhodes, and Col. Burgoyne. The result of these reports 

 may be stated in a few words, namely. That the Shannon may 

 be considered as a combination of lakes and rivers, from its 

 source in Lough Allen to the sea below Limerick : 



The total distance from Limerick to Lough Allen is 144 miles : 



The total height of the mean surface of the water in Lough 

 Allen above that of the surface at Limerick is 143 feet seven 

 inches, which gives an inclination of rather less than twelve 

 inches in a mile : 



The natural fall is, however, reduced to a series of horizontal 

 planes of diff"erent lengths by locks : 



The general direction of the river is extremely irregular, and 

 broken by many streams, islands, and rocks : 



The soundings vary in the same manner, and in some places 

 are very deep, in others very shallow : 



The river is liable to be overflowed to a great extent on both 

 banks, and the large expanse of the lakes renders the vessels 

 which navigate the river unfit for the lakes : 



The works which have been constructed to overcome the 

 natural difficulties of the navigation are either insufficient or in 

 a state of decay ; and it seems to be generally admitted that very 

 little real good can be effected until the natural obstructions are 



