7 88 Proceedings of Royal Society of Edinburgh. [sess. 
Inch. 
Inch. 
2 a.m. -0*012 
4 „ - 0-022 
6 „ 0 003 
8 „ 0-028 
10 „ 0-032 
2 p.m. -0-043 
4 „ - 0-055 
6 „ -0-028 
8 „ 0-004 
10 „ 0013 
Noon, 0*006 
Mid. 0-012 
from which it is observed that the amplitude of the range from the 
morning maximum to the afternoon minimum amounts to 0°'087 
inch. 
Latitude for latitude, the smallest variations over the open sea 
occur in the anticyclonic regions of the different oceans. Thus 
about lat. 36°, and the time of the year when the sun is highest in 
the heavens, the amounts are — for the South Pacific, 0 036 inch ; 
North Pacific, 0'025 inch; South Atlantic, 0-024 inch ; and North 
Atlantic, 0*014. It thus appears that these amplitudes diminish 
as the ocean is more land-locked with continents. 
In the open ocean the morning minimum of pressure is largest 
in equatorial regions, and it diminishes with latitude ; but the rate 
of diminution with latitude, through anticyclonic and other regions, 
is generally less, and is more uniform than is the case with the 
afternoon minimum. Further, in high latitudes over the open sea, 
the diurnal barometric tide shows only one maximum and one 
minimum ; and also in continental situations in high latitudes there 
occurs in summer only one maximum and one minimum, but the 
phases of their occurrence are the reverse of each other. 
In middle and higher latitudes in summer, proximity to the sea, 
conspicuously so when the places are situated on the west coasts of 
continents and islands, delays the time of occurrence of the morning 
maximum and the afternoon minimum ; whilst in continental 
situations the morning maximum occurs much earlier than in lower 
latitudes, and the afternoon minimum nearly as late as at places 
near the sea. But, as seen from the “ Challenger ” observations, these 
peculiarities of the curves do not occur over the open sea in the 
higher latitudes. The retardation of the time of occurrence of the 
morning maximum is greatest in situations which, while strongly 
insular in character, are at the same time on, or not far from, an 
