232 
THE PHYSICAL GEOGRAPHY OF THE SEA. 
mense pennon jfloating gently in the current, such a motion as such 
a streamer may be imagined to have — very much such a motion — 
do my researches show the tail of the Gulf Stream to have. Run- 
ning between banks of cold water 1), it is pressed now from 
the north, now from the south, according as the great masses of 
sea matter on either hand may change or fluctuate in temperature. 
493. In September, when the waters in the cold regions of the 
north have been tempered, and made warm and light by the heat 
of summer, its limits on the left (Plate VI ) are as denoted by the 
line of arrows ; but after this great sun-swing, the waters on the 
left side begin to lose their heat, grow cold, become heavy, and 
press the hot waters of this stream within the channel marked out 
for them. 
494. Thus it acts like a pendulum, slowly propelled by heat on 
one side and repelled by cold on the other. In this view, it be- 
comes the chronograph of the sea, keeping time for its inhabitants, 
and marking the seasons for the great whales ; and there it has 
been for all time vibrating to and fro, swinging from north to south 
and from south to north, a great self-regulating, self-compensating 
pendulum. 
495. In seeking information concerning the climates of the 
ocean, it is well not to forget this remarkable contrast between its 
climatology and that of the land, viz. : on the land, February and 
August are considered the coldest and the hottest months ; but to 
^ the inhabitants of the sea, the annual extremes of cold and heat 
occur in the months of March and September. On the dry land, 
after the winter " is past and gone," the solid parts of the earth 
continue to receive from the sun more heat in the day than they 
radiate at night, consequently there is an accumulation of caloric, 
which continues to increase until August. The summer is now 
at its height ; for, with the close of this month, the solid parts of 
the earth's crust and the atmosphere above begin to dispense with 
their heat faster than the rays of the sun can impart fresh sup- 
plies, and, consequently, the climates which they regulate grow 
cooler and cooler until the dead of winter again. 
496. But at sea a different rule seems to prevail. Its waters 
are the store-houses in which the surplus heat of summer is stored 
away against the severity of winter, and its waters continue to 
grow warmer for a month after the weather on shore has begun 
