TIDAL OBSERVATIONS. 



133 



Referring to the annexed diagram (A) to illustrate the numerical method, the 

 mean reading of two sv:ccessive high waters is taken and placed opposite the read- 

 ing of the intermediate low water (see series of upper circles in diagram), next the 

 mean of these successive values is placed opposite the intermediate high water. In 

 like manner the mean of two successive low waters is taken and placed opposite the 

 intermediate high water (see series of lower circles in diagram), and their means 

 again are taken ; we thus obtain on each horizontal line two values, one high the 

 other low, exactly corresponding in epoch, the mean of which is that of the half- 

 tide level as set out in the last column, thus : — 



Date. 



Phase. 



Readings. 



Means. 



Means. 



Half tide level. 



1861. July 2 



L. 



16.0 











H. 



18.6 





15.05 







L. 



14.1 



19.35 



15.05 



11".1T 





H. 



20.1 



19.30 



15.05 



n.n 





L. 



16.0 



19.25 



15.05 



17.15 





H. 



18.4 



19.35 



15.05 



17.20 





L. 



14 1 



19.45 



14.80 



17.13 





H. 



20.5 



19.35 



14.55 



16.95 





L. 



15.0 



19.25 



14.3T 



10.81 





H. 



18.0 





14.20 







L. 



13.4 



etc. 







The following table contains the date, time of high or low water, and correspond- 

 ing height (corrected if necessary in accordance with preceding remarks), and the 

 half-tide level as made out by the above process ; the remaining columns contain 

 the moon's declination at noon of each day, also the moon's parallax for the same 

 epoch, together with the atmospheric pressure (reduced to the temperature 32° Fah., 

 and the prevailing direction and force of the wind during each day. 



Table I. — Observed times and heights of high and low waters at Port Foulke, latitude 78° 17'. 6, 

 longitude 4'' 52™ O'' west of Greenwich. Also the corresponding half-tide level, the moon's decli- 

 nation, the moon's paralla.x, the atmospheric pressure (at the temperature of the freezing point 

 of water), and the true direction and force of the wind. 







s 



eries I. 



ISTovc ruber 



and December, 1860. 









Date. 



High 

 01- low 

 tide. 



Observed 

 mean time. 



Morning 



or 

 afternoon. 



Observed 

 height 

 in feet. 



Deduced 



half-tide 



level. 



Moon's 

 declina- 

 tion. 



Moon's 

 paral'x. 



Atraos. 

 press. 



Direction 



of 



wind. 



Force 



of 

 wind. 



Nov. 17 



H. 

 L. 



2" 25'" 



9 05 



A. 

 A. 



16.4 



8.2 







— 21C.0 



56 '.4 



29'". 7 



calm 





18 



H. 



2 50 



M. 



1.3.6 



11.85 













" 



L. 



9 30 



M. 



9.6 



11.80 



—17.2 



55.7 



29.9 



N. E. 



3 



" 



H. 



3 25 



A. 



15,6 



















L. 



10 00 



A. 



8.6 

















19 



H. 



.... 



M. 





















" 



L. 



.... 



M. 











—12.6 



55.0 



29.8 



N. E. 



4 



" 



H. 



4 30 



A. 



14.7 

















" 



L. 



10 15 



A. 



7.7 



.... 













20 



H. 



4 45 



M. 



12.0 



















L. 





M. 







.... 



—7.7 



54.6 



29.9 



N. E. 



1 





H. 





A. 



. . . 

















" 



L. 



10 45 



A. 



8.1 

















