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and laws of the Tides on the coasts of Ireland, — the more important 

 questions that present themselves, as demanding further investiga- 

 tion, are the following : 



" 1. The law of the diurnal tide, referred to the actions of the 

 two luminaries, and the separation of the effects due to each. 



" 2. The apparent anomalies in the progress of the diurnal tide- 

 wave, and the variations of its range. 



" 3. The phenomena connected with the progress of the semi- 

 diurnal tide-wave in the Irish Channel, and its supposed inversion. 



" 4. The proof from observation of the existence of a tertio- 

 diurnal tide, as indicated by theory. 



"5. The apparent difference in the heights of mean water, on the 

 north and south coasts of the Island, as well as in large and small 

 tides. 



"Owing to the complexity in the law of the rise and fall of the 

 tide, and its variations at different places, the system of observation 

 required in the solution of these questions is necessarily an elabo- 

 rate one. The whole course of the tide must be followed, by ob- 

 servations at short intervals ; but, as so great an amount of labour 

 could not be expected continuously, it is proposed that the four 

 principal tides in each lunation only (the two spring and two neap 

 tides) shall be observed in this manner, — the observations being 

 continued at intervals of a quarter of an hour for twelve hours. In 

 addition to these weekly observations, daily observations of the 

 greatest and least heights of the tide (without reference to time) will 

 be obtained by the help of a self-registering apparatus. 



"Your Council have prepared a body of instructions, based upon 

 the foregoing principles, in'which the rules as to the times, and all 

 the other details of the method of observation, are fully explained. 



"The instruments required at each station for these investigations 

 are, a barometer, a pair of ordinary thermometers (dry and wet 

 bulb), a pair of self-registering thermometers, a wind vane, Lind's 

 anemometer, and a rain-gauge. In addition to these, a self-register- 

 ing tide-gauge will be required at the tidal stations, and a ther- 

 mometer adapted to the observation of the temperature of the 

 sea. The details connected with the form and construction of these 

 instruments have been fully considered by the Committee of Science; 



