352 Prof. A. D. Bache on Tidal Observations. 
TABLE No. VIIL Dracram No. 6. 
Showing the — from the comparison of computed and observed ordinates of 
* 
iurnal curves, classed according to the ages of the moon 
Hours of moon’s | RESIDUALS. 
transit. First six months, Second six months, Mean, 
of “33 “aa 
134 “17 “32 13 
2g “y “15 15 
3 “ “12 “13 
43 - “00 -08 
58 “of —o3 "02 
64 » -of —-03 “OI 
74 me —02 +63 
84 13 “04 08 
93 “32 “33 12 
104 "09 “14 “II 
tig “19 “14 16 
These residuals, instead of following the law of cos(w—¢), fol- 
low that of cos(2y — 2), or that of the semidiurnal curve. 
Before examining this result, which is shown in Diagram 6, I 
ss to the residual which results from carrying on the former 
table to 233 hours; which was in fact the form of the table be- 
fore the development of the law of variation showed that the term 
for 123 hours belonged to 04, instead of 114, with which it would 
agree if the law of cos(w—@) were followed. The following 
8 contains the residuals in question, shown also in Diagram 
No. 7. 
TABLE No. IX. 
Showing residuals after deducting those following law of change of 
cos (2 — 29). 
Age of moon. Residuals, Reviduals. Mean. 
hours. feet, hours. feet. 
—°O7 234 . ~—--Ol 
14 —*02 224 —-Ol 
24 OI a1 OL 
3} 03 204 “03 
48 “00 194 "02 
54 : ‘Ol 184 “04 
64 05 175 -08 
74 “04 164 “09 
84 “OF 154 -o4 
“02 144 +00 
tos —°o3 134 -o3 
114 -o3 124 -06 
Mean.... *o3 
The existence in the first residuals of the law belonging to the 
semidiurnal curve indicates that the separation of the two curves 
(diurnal and semidiurnal) is not complete, as indeed the hypothe- 
sis of a constant difference in time between the recurrence of the 
two maxima requires. Before undertaking to modify this hy- 
pothesis, I proceed to inquire whether these numbers would re- 
