80 U. S. COAST AND GEODETIC SURVEY 
M,, Py, and Q,, and to the semidiurnal constituents K, L:, and v2, and 
formulas (326), (328), (329), (332), (833), and (342) were used for the 
purpose. The following results were obtained for the differences 
between values as obtained from inference and from observations. 
The average gross difference is the average difference without regard 
to the signs of the individual items, and the average net difference 
takes into account these signs so that a positive difference may offset 
a negative difference in the mean. The last two lines in the table 
show the percentage of cases in which the differences were less than 
0.05 and 0.10 foot, respectively, for the amplitudes, and less than 10° 
and 20°, respectively, for the epochs. 
Ft. Deg. Ft. Deg. Ft. Deg. 
Vila GieNeM CO eee eee ee ee es 0. 05 149 0. 27 49 0.05 105 
Awverace eross\difteClen COssssner sean ene eee . 02 31 . 03 8 01 14 
Mveracemeti@inleren Cet eee a= ae eae mee nee eee 01 1 01 3 . 00 0 
% % % % % % 
Differences less than 0.05 foot or 10°.....-.....-.------ 93;|.o.1 B@thwer: 86/9 [76s| ee 96 ia es 
Differences less than 0.10 foot or 20°_____-__------------ 100 57 92 92 100 82 
Ko Le v2 
ampli Ke ampli- 12 ampli va 
Ft. Deg. Ft. Deg. Ft. Deg. 
INfeeeihaliron Gene a) 2 ee ee nate mee 0. 28 51 1.09 104 0. 28 53 
Average gross differences. -=---222--a--2-- eae — naa . 02 9 . 09 25 . 04 14 
iMcenase met qineremcCe ssa =o sane eee oe ea . 00 5 . 08 4 . 02 4 
Ty. || Cox | | Gl\\S See) Geel ee 
Differences less than 0.05 foot or 10°_-_-_..------------- 87 65 58 20 71 48 
Differences less than 0.10 fost or 20°___---.------------ 97 93 7 44 88 83 
By using formulas (334) and (343) for L, and » the results are 
slightly improved, the average net differences for the amplitude and 
epoch of L, becoming 0.07 foot and 3°, respectively, the difference for 
the epoch of vy, becoming 2°, while the average net difference for the 
amplitude of ». remains unchanged. 
234. Although there is a fairly good agreement indicated by the 
average differences, it is evident that the inferred constants, especially 
the epochs, cannot be depended upon for a high degree of refinement. 
It may be stated, however, that for constituents with very small 
amplitudes the epochs determined from actual observations may be 
equally unreliable. This becomes evident when results from different 
years of observations are compared. Fortunately, the large dis- 
crepancies in epochs are found only in constituents of small amplitude 
and are therefore of little practical importance. 
235. Constituent 2 as determined by inference is relatively unim- 
portant. However, this constituent has the same period as_ the 
compound tide 2MS, and when obtained directly from the analysis 
of observations frequently differs considerably from the inferred py: 
both in amplitude and epoch. The inferred values for this constituent 
cannot therefore be considered as very satisfactory. 
236. Prior to the elimination process described in the next section, 
certain preliminary corrections are applied to the amplitudes and 
