TIDAL OBSERVATIONS. 377 



L. Speed (2y-(T-w). N. Speed (2y-3ff+-nr). 



1858-59. 1859-60. 1860-Gl, 1858-59. 1859-60, 1860-61. 



E^ o'o59i 0-0370 0-0506 o'393i °'3494 °"3545 



(•3 io2°-63 i83°-oo i7o°-i6 303°-46 3°5°'53 302°-5i 



E. Speed (2y-,,). T. Speed (2y-3/j). 



1858-59 and 1859-60. 1858-59 and 1859-60. 



K3 o'ooyS R^ o'oi4z 



e.y i64°-oo 6, 277°'90 



\. Speed(2y-ff+TO— 2)/). v. Speed (27- 3(r-T!r + 2»j). 



1858-59. 1859-60. 1860-61. 1858-59. 1859-60. 1860-61. 



E^ 0-0372 0-0275 0-OI2I 0-1044 0-0387 o'o437 



Cj i88°-3o i56°-39 i44°-i8 287°-23 zyz^-^e 349"-59 



fi or 2MS. Speed 2(y-2cT+);). 



' ' N 



1858-59. 1859-60. 1860-61. 



E^ 0-0257 0-031 1 0-0252 



•="2 254°'34 2o6"-i4 209°-53 



J. Speed (y+ff— -or). Q. Speed (y — off+w). 



1858-59. 1859-60. 1860-61, 1858-59. 1859-60. 1860-61. 



Ej 0-0819 00376 0-0565 0-1706 0-1056 0*1332 



ei 2i3°-98 2o8°-29 183^-40 353°'03 33i°'34 ^°'9Z 



35. Here, again, we have an abrupt diminution in tlie height of mean level 

 for the first two years, which the following extract from a letter received 

 from Prof. J. E. Hilgard, fixUy explains : — 



" The change in the mean-level reading at Fort Point is a matter of much 

 " annoyance to us. The tide-gauge was put up in a small building near the 

 '•■ end of a wharf, and the tide-staff used for comparison was close to it, Now 

 " it was observed after the observations had continued some time that the 

 " wharf was settling, — at least the part where the gaiige stood. Then the 

 " gauge was moved to a point a little nearer to the shore believed to be firm, 

 " but we think the whole wharf settled and continued to do so for years. 

 " There seems to be a bog formation underlying the surface deposit at that 

 " place. There is probably no way of ascertaining the amount of settling 

 " except from the observations themselves. We are now having frequent 

 " levellings made, referring the tide-staff to a rocky ledge further inland." 



36. It having come to the knowledge of the Tide Committee that the United 

 States Coast Survey OiRce was in possession of a series of hourly tide observa- 

 tions taken at Cat Island in the Gulf of Mexico, and which were of a very 

 remarkable and interesting character, it was thought a favourable opportunity 

 of testing the value of the harmonic analysis for the evaluation of the com- 

 ponents of the tides of this place, which appeared very complicated and pe- 

 culiar. Application having been made, a series of about thirteen months 

 Avere received through the kindness of Prof. J. E. Hilgard. 



The following results represent the tide-components as far as they have at 

 present been evaluated. Datum 10 feet beloiv datum of United States Coast 

 Survey: — 



