Diurnal Tides of the Coasts of Ireland. 51 



XII. Dunmore East, Co. Waterford. 

 Lat. 52° 8' N. Long. 6° 57' W. 



The tide-gauge was erected at the inner angle of the harbour 

 in a very sheltered position. 



Its zero was referred to the copper bolt driven vertically into 

 one of the facing-stones of the pier, not far from the light-house. 

 It was found to be 17*59 feet below this bolt. 



The twelve tidal stations just described M'ere established be- 

 tween September 1850 and January 1851, and were each visited 

 twice during the observations. 



The time was found at each station by means of a vertical 

 gnomon, with a meridian line, the observation of which at mid- 

 day, with the aid of a table of the equation of time furnished to 

 each observer, gave the local time with considerable accuracy. 



The tide-gauge consisted of a wooden case, from 20 to 28 feet 

 in length, placed in a vertical position and closed at the bottom, 

 excepting a few holes, guarded by copper gauze. The bottom of 

 the case was placed 4 or 5 feet below low-water mark, and the 

 oscillations of the water outside were scarcely sensible within the 

 case. To the top of the case was attached a box containing a 

 drum, over which was passed a silk cord, terminating at one 

 extremity in a wooden float resting on the water, and at the other 

 extremity in a small leaden counterpoise. The motion of the 

 water inside the case was communicated by this cord to the drum, 

 which was connected by wheel-work of a very simple character 

 with the index-hand of a dial, marked into sixteen feet, each 

 divided into tenths. 



These dials and the annexed wheelwork wei'e made by Mr. 

 Dobbin, of AVicklow Street, Dublin, and worked remarkably well 

 during the whole time of being used. In addition to the index- 

 hand traversing the dial, two other hands were placed on a separate 

 axle, which were pushed in opposite directions by a projection 

 placed on the index-hand, thus registering without observation 

 the maximum and minimum heights of the tide. To obtain this 

 registry it was only necessary to visit the dial twice during each 

 lunar day, either at half-flood or half-ebb ; and after a few days' 

 practice, no difficulty was experienced by the observers in record- 

 ing all the high and low waters, with a very slight expenditure 

 of time. 



The greatest care was taken to secure accurate determinations 

 of the exact position of the zei'o marked outside the case, with 

 reference to the Ordnance and other bench-marks, the zero of 

 the dial being made to correspond with the zero outside. The 

 gnomons by which the time was observed were also erected with 



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