355 
The calculations founded on the last two methods gave 
respectively 11°9 miles and 11°3 miles, each result being a 
mean of those derived from eight stations, agreeing remarka- 
bly well with each other. 
The calculation founded on heights gave as a result a 
depth of 5:12 miles, agreeing with a result deduced by La- 
place from the long series of Brest observations on the semi- 
_ diurnal tide, viz., 5-07 miles. 
Mr. Haughton was of opinion that the first result, viz., 
11°6 miles, is the depth of the central channel of the South 
Atlantic, up which the tide waves advance from the Antarctic 
Ocean ; while the second result, viz., 5 miles, deduced from 
heights, represents the mean depth of the whole Atlantic Ocean, 
including the shallow water of the soundings in the eastern 
portion, near the British Islands. This view he considered to 
be confirmed by the great age of the diurnal tide, viz., five to 
_ six days,—a circumstance which shows the great distance from 
the coast at which the tide wave is formed, which gives the 
character to the diurnal tides of the Irish coasts. 
