27 



As an example of the use of the construction I have given, let us 

 take the case of the mail- steamer from Kingstown to Holyhead, at 7 p. m. 

 this evening. 



This steamer leaves Kingstown at 7*" 25™ Greenwich time, and ex- 

 pects to arrive at Holyhead at IP 25°". The High Water at the Head 

 of the Tide to-night will take place at 6^ 42"^ Greenwich time. There- 

 fore the Tidal Hours of the steamer's departure and arrival are — 



Departure from Kingstown, .... XII'43°' 

 Arrival at Holyhead, ...... iy-43 



Taking the maximum rate of stream between Kingstown and Holyhead 

 at 3 knots per hour, and making the construction I have pointed out on 

 the circle of 6 knots radius, we find that the Ebb Tide will drift the 

 steamer 7*8 knots to the southward of Holyhead Harbour, unless a cor- 

 rection be applied in steering. (Mr. Haughton here exhibited a Tidal 

 Card, by means of which the rise or fall, and the tidal drift, could be cal- 

 culated for any case in a few moments.) (Tide Plate II.) 



This is nearly the greatest amount of Tidal Drift that the Kingstown 

 and Holyhead steamers are subject to. Their greatest drift is 8*16 

 knots, which will occur to the South, when their times of departure and 

 arrival are I. and Y. by the Tidal Clock; and 8*16 knots to the JN'orth, 

 when their hours of departure and arrival are YII. and XI. by the 

 tide. There is, therefore, in this four hours' run, which is made at 

 the rate of 1 6 miles per hour, a possibility of the steamer finding her- 

 self, if she neglect the Tidal Stream, 9 miles to the north or to the south 

 of Holyhead or Kingstown. In a fog, when the passage is delayed, it 

 has sometimes happened that these steamers have found themselves off 

 Bray or Dalkey Sound, when they supposed they were close to the mouth 

 of Kingstown Harbour. The Tidal Stream in the Irish Sea is greatly 

 modified by the wind, which, if northerly, will cause the Ebb Tide to 

 carry out more water than its proper share past the Tuskar entrance ; 

 and, vice versa, the wind, if southerly, will aid the Ebb Tide through the 

 JSTorth Channel, and seriously embarrass vessels beating to the south- 

 ward. 



This complication of the tides caused by the wind has not yet re- 

 ceived the amount of attention its importance merits ; and it is well 

 expressed in the following statement, which I have received from Mr. 

 J". Bowling, Master, E. in command of H. M. tender, " Badger," 

 whose long experience in the Channel entitles his opinion to much 

 weight : — 



''H. M. Skip Badger, June 12th, 1861. 

 It has occurred to me that there was a point of some importance in 

 direct connexion with the subject of the tides, namely, the great diffe- 

 rence which must exist between the strength of the succeeding flood 

 and ebb-tides, with strong prevailing winds up or down channel. 



Take, for instance, from the Saltee Islands [to Holyhead, within 

 which bounds it is a well-known fact, that the tides rise much higher, 

 and continue to flow much longer with strong winds up channel, than 



