52 



at this station and at the period of the observations may be arranged 

 as follows : 



(1) Hourly heights Ao-ftn 11- 55 12.77 13.21 12.82 11.51 9.9? 8.27 7.03 



(2) Hourly heights fti2-/i23 11. 54 12.76 13.32 12.89 11.77 9.99 8.34 7.12 



6.46 

 6.51 



6.79 

 6.81 



8.06 

 8.15 



9.72 



<3) Sums 23.09 25.53 26.53 25.71 23.28 19.91 16.61 14.15 12.97 13.60 18.21 19. 



(4) Sums fte to /ill 16.61 14.15 12.97 13.60 16.21 19.68 



<5) Differences 



11.38 13.56 12.11 7.07 



log S2 

 10gC2 



log tan f 



log «2 



log sin f 



log M2 



M2 



= 0.47448 

 = . 20820 



= . 26628 

 = 61°. 6 

 = . 47448 

 = 9.94414 



= . 53034 

 = 3.391 



23. 115 

 -3. 734 



12C2 = 



19.381 

 : 1.6151 



35. 781 



12S2=35. 781 

 S2= 2.9818 



^n=- 



The expression for the M2 component is therefore: 



2/=3.391 cos (m2^-61.6°) 



Figure 26 shows the graph of the M2 component and the plotted 

 heights (referred to mean sea level) of the resultant of all of the M 

 <jomponents as derived. It is apparent that at this station the other 



l( 



bD — \ 



2 -2- 

 -3 - 



.0 



--O^ 



o' 



-o>.. 



*o 



\ 



o 



°^o-^ 



\s 



15- 



\ 



le 



.^o 



ai 



e4 



Lunar Hours. 



Figure 26.— M2 component and hourly values of M group, Sitka, Alaska. 



components of the group are small and that the summation has 

 nearly effected the elimination of components outside of the M group. 



It is of interest to note that in the computation as set forth, the 

 summation of lines (1) and (2) automatically eliminates the Mi and M3 

 components, and the subtraction of line (5) from line (4) eliminates the 

 <ionstant height of mean sea level and the M4 and Mg components. 



96. A reference to the list of components in paragraph 75 shows 



