132 Facts in Meteorology. 
no means subject to such extremes as the latter. ‘The temperature 
of the sea never, in any latitude, exceeds 86 or 87 degrees of 
Fahrenheit. 
The existence of banks or shallows has a local effect in diminish- 
ing the temperature of the ocean, but the great agents in modifying 
it are currents, which mingle together, or, rather, change the locality 
of waters of different regions. Thus, the gulf stream, as it is called, 
which sets into the gulf of Mexico from the equatorial regions, is 
much warmer than the neighboring parts of the sea; the current of 
Chili is just the reverse, being in its progress from the higher to the 
equatorial latitudes, where it passes into the wide Pacific, and car- 
ries the warmth which is subsequently — again to the higher 
latitudes. 
’ Of Tides. 
The influence of the moon in producing the tides, is supposed to 
be greater than that of the sun, and evidently governs the time of 
high water. As the moon crosses the meridian of a place about 
every twenty-four hours and fifty minutes, the sea, in most parts of 
the world, ebbs and flows twice in that space of time. In large 
rtions of the Pacific Ocean, however, as well as in certain other 
localities, the tides are exempt from the lunar influence. At Ta- 
hiti and the Georgian group, near the center of the Pacific Ocean, 
the tide rises but one or two feet, and it is high water at noon and 
midnight a the year, and this too, in the very region where 
the hed theory would lead us to expect the lunar tides to be 
the most seatar and powerful. The tides upon the coast of Guate- 
mala, in the Caribbean sea, afford a similar exception, while on the 
opposite coast at Panama the tides of the Pacific rise to the height of 
twenty feet. These facts serve to show that the modus operandi of 
the causes which produce tides, is not thoroughly understood.* 
* Does not the course of the great semi- diurnal, tine wave, in each of the great 
oceans, mainly correspond to the great ic and atmospheric currents, 
west to east in the higher latitudes? Mr. Lubbock, who is engaged 
in an elaborate investigation of the facts in relation to the tides, ean furnish us the 
ineans of solving this question. If the affirmative be true, these several movements 
would seem to originate in a common impulse or tendency. 
