RECORD AND REDUCTION OF THE TIDES. 



69 



o^ 30", 6'' 30"', 7'' 30'", Avherc the curve is steepest ; the value — is obtained from 



the greatest range of the inequality determined, for a first approximation, by a 

 graphical process. I find from the observed high waters a = 0'' 21"" or 5° 15', and 

 from the low waters a = 0'' 50'" or 12° 30'. Kange of inequality, from the high 

 waters, 1'' 51"" or 27° 48', the sin. of which is 0.4649, and for the low waters, range 

 l*" 54"° or 28° 30', the sin. of which is 0.4771 ; hence the expression for the half- 

 monthly inequality in time becomes 



From the observed high waters tan. 2(0'— 175°49'.5)=— ^"^^^^^ ^"'- ^ (<?> — 5° IgO 

 " ^ ^ l + 0.4649co5.2((?)— 5°15') 



» « u 1 4- * r,,n> crionn,\ 0.4771 sm. 2 (d) — 12° 30') 



" " " low waters tan. 2 (6 — 26 i° 00')= — i-l ^ 



^ ^ 1+0.4771 COS. 2 (<?)— 12° 30' 



These expressions furnish us with the following comparison : — 



HALF-MONTHLY INEQUALITY IN TIME. 



) 



Considering that the times of high and low water are only observed to the 

 nearest half hour and for some time to the nearest hour, the agreement as shown 

 above and by the diagrams, seems to be satisfactory. 



Observed and computed half-monthly inequality in time for ohservations. 

 Of the high waters. Of the low waters. 



+11' 00" 

 50 

 40 

 30 

 20 

 10 



10 



20 

 30 

 40 

 50 

 _lh 00- 



0" 1 2 3 4 5 6 7 8 9 10 11 12'' 



0" 1 2 3 4 5 6 7 8 9 10 11 121' 



30"' 



30'" 



30"' 



H l( tt tl 



(( (( (( (( (( It 



30"' 



