222 



REPORT — 1879. 



List of various Local Datum Marks, &.C. — continued. 



Ireland. 



Ordnance Datum 

 of Ireland 



Belfast . 



Dublin . 



Hawlbowline 

 Island, near 

 Queenstown 



i,.\v. of Spring Tides in Dublin Bay, 

 being 20-90 below a mark on the base 

 course under the south window of 

 Poolbeg Lighthouse. Supposing mean 

 sea level on English Coast to be the 

 same, the above datum is 8094 ft. 

 below mean level of sea round Ire- 

 land, which is 0-623 ft. above Ordnance 

 datum of Great Britain. The Irish 

 Ordnance datum is, therefore, 7'46 ft. 

 below that of Great Britain 



Harbour datum, level of No. 2 Old 



Graving Dock sill. 

 Port of Dublin, north wall, standard 

 Floor of New Graving Dock . 



Ordnance Datum 

 of Ireland 



Feet 



Above 

 2-92 



1-43 



Below 



22-30 



Authority 



T. R. Salmon. 



P.. B. Stoney. 

 C. Andrews. 





