378 . REPouT— 1873. 



Cat Island, Gulf of Mesioo (Lat. 30°-23 N., Long. 6''-94 W. of Greenwicli). 



Year 1848. Ao=4-8s74ft. I=i8°-45. 

 S M L N 



Speed (y-n) (r-0 {r-i<T-i-sr) (y— |(t+4w) 



Kj^ o'044z o-oioi 



6j io°o4 9S°"5'i 



Kg 00677 o'ii95 o-oii8 0-0269 



£2 23°'8o io°'75 222°-4o 33°'57 



K O P J Q 



Speed (y) (y-2<7) (y-2);) (y+ff-'ST) (y-3(T+-BT) 



Ej 0-4627 o'38ss o'iSS9 0-0292 o'o733 



6^ 5S°'2o 224^-29 23o°-65 28°-22 2i5°-3a 



E3 0-0205 



63 288°-73 ...... 



37. It is extremely intrestiug to fmd that, although the lunar and solar 

 semidiurnal tides are very small in value, the series of means from which 

 they -were obtained being extremely rcgTilar and good, the consequent deter- 

 mination of the phase of spring-tides (§ 50) from their respective epochs is 

 probably correct -svithiu a few minutes. The proportion between the ampli- 

 tudes of the lunar and solar semidiurnal tides is the nearest approach to 

 equality yet obtained, being in the ratio of 11 to 6. The comparatively large 

 value of Rj of Series S is undoubtedly a genuine tide, but the smallness of the 

 corresponding value of Series M must forbid the conclusion of its being purely 

 astronomical. It is perhaps produced by temperature or -nind, its time of 

 maximum being about 40 minutes after noon. There are also indications of 

 a similar and large annual tide of 0-27-1 foot amplitude, and maximum about 

 Aug. 16, which is also probably meteorological in its origin. The proportion 

 between the lunar and solar diurnal (Declinational) tides (R^ of Series 

 and P) wUl be, on the assumption of the variation of E^ of Series being as 

 the square of the sine of the declination, about 4 to 1 . 



38. The following are the v.alues of the long-period tides : — 



E G 



ft. 



Solar annualtide (elliptic and meteorological) 0-274 I44'5° 



Solar semiannual tide (declinational and meteorological) ... o'i28 35'oa 



Lunar monthly tide (elliptic) 0-106 304-17 



Lunar fortnightly tide (declinational) o'043 136-69 



Lunisolar fortnightly tide (synodic) 0-099 33626 



39. Professor FuUcr having applied to Mr. Parkes for a set of tide-obser- 

 vations of any port in India, that gentleman kindly placed at the disposal of 

 the Committee, for analysis, a series of personal tide observations taken at 

 Bombay from January 29, 1867 to June 4, 1867. The heights were observed 

 at successive intervals of ten minutes, and were taken under the superin- 

 tendence of Mr. Ormiston, C.E. A few breaks of short duration in the 

 observations have been supplied from a curve plotted for each day of inter- 

 rupted observation. The datum-line is 72 feet below the level of the 

 Town-HaU datum. 



40. The observations were not used as they were given, but heights for 

 each quarter hour, the heights for the fifteen and forty-five miautes past each 

 hour being interpolated. Tables similar to those previously described (§ 16), 

 but adapted for the reduction of observations taken for every quarter hour, 

 have been made for a period of 127 days. 



