THE TIDES. (APP. C) 207 



equality presented by tidal observations which had 

 been made at Freemantle, Western Australia, in 

 1873-74, chiefly by Staff-Commander Archdeacon, 

 R.N., the officer in charge of the Admiralty Survey 

 of that Colony. The results disclosed very re- 

 markable complications, the diurnal tides pre- 

 dominating over the semi-diurnal tides at some 

 seasons of month and year, and at others almost 

 disappearing and leaving only a small semi-diurnal 

 tide of less than a foot rise and fall. These 

 observations were also very interesting in respect to 

 the great differences of mean level which they 

 showed for different times of year, so great that 

 the low-waters in March and April were generally 

 higher than the high-waters in September and 

 October. The observations were afterwards, under 

 the direction of Captain Evans and Sir William 

 Thomson, submitted to a complete harmonic 

 analysis worked out by Mr. E. Roberts. Not only 

 on account of the interesting features presented by 

 this first case of analysis of tides of the southern 

 hemisphere, but because the south circumpolar 

 ocean has been looked to on theoretical grounds as 

 the origin of the tides, or of a large part of the 

 tides, of the rest of the world, it seemed desirable 

 to extend the investigation to other places of the 

 southern hemisphere for which there are available 

 data. Accordingly the records in the Hydrographic 

 Office of tidal observations from all parts of the 

 world were searched, but besides those of Free- 



