SEA WATER
219
for it has been estimated that there exists dissolved in the
_
oceans 46,700 times as much silver as has been minéd all
over the world between 1902
of America
by Columbus, in 1492.
This is, in all, I 3,300 million tons,
but it would be a very tedious matter to extract it !
'
But the most important bodies di500vered in sea water
are certain manurial salts which are only presentin very
' —
minute quantities. These are the phosphates and the
nitrates, substances which we» know have a very great
nutrient value in the soil on land-and are among the chief
components of all natural or articial manhres.
'
We have mentioned in _a previ0us chapter (page 114)
that in the sea, as well as on the land, all life is ultimately
dependent on the plants for its supply of food. In.the
_
off—shore waters of the sea the plant life is represented
-
.
almost solely by that great drifting cOmmunityof plankton
plants among which- the minute, unicellular diatoms -are
themost numerous.
It is on the nutrient salts present in
_
solution in the sea that these diatoms depend for their
_
food.Onland the plant extracts phosphates “and
nitrates
_
from the soil by means of its roots;
The ne “
root hairs ”
abSorb' the nourishing salts from . the minute interstices
among the soil—,particles’wherethe=moisture holds them in
solution.
In the case'of diatoms; however, there is no need
of any Specialized structure such as the root to take up these
valuable
for its whole body is bathcd in the sea
water-from which
food-is absorbed.”
More willbe said
in the next chapter On this subjæt-and-the effects of" the
'
presence-or absence of the manurialsalts on the seasonal
cycle of
in the sea:
'
-
Besides thèse “ solid -’Î salts inthe- sea there are also
._'
present» certain gases_ dissOlvèd in the Water;
_
Animals
_
cannot live without oxygen…— We extract :the. oxygen that,
we breathe in with
airinto our lungs, and .itis’ carriè‘d
219
for it has been estimated that there exists dissolved in the
_
oceans 46,700 times as much silver as has been minéd all
over the world between 1902
of America
by Columbus, in 1492.
This is, in all, I 3,300 million tons,
but it would be a very tedious matter to extract it !
'
But the most important bodies di500vered in sea water
are certain manurial salts which are only presentin very
' —
minute quantities. These are the phosphates and the
nitrates, substances which we» know have a very great
nutrient value in the soil on land-and are among the chief
components of all natural or articial manhres.
'
We have mentioned in _a previ0us chapter (page 114)
that in the sea, as well as on the land, all life is ultimately
dependent on the plants for its supply of food. In.the
_
off—shore waters of the sea the plant life is represented
-
.
almost solely by that great drifting cOmmunityof plankton
plants among which- the minute, unicellular diatoms -are
themost numerous.
It is on the nutrient salts present in
_
solution in the sea that these diatoms depend for their
_
food.Onland the plant extracts phosphates “and
nitrates
_
from the soil by means of its roots;
The ne “
root hairs ”
abSorb' the nourishing salts from . the minute interstices
among the soil—,particles’wherethe=moisture holds them in
solution.
In the case'of diatoms; however, there is no need
of any Specialized structure such as the root to take up these
valuable
for its whole body is bathcd in the sea
water-from which
food-is absorbed.”
More willbe said
in the next chapter On this subjæt-and-the effects of" the
'
presence-or absence of the manurialsalts on the seasonal
cycle of
in the sea:
'
-
Besides thèse “ solid -’Î salts inthe- sea there are also
._'
present» certain gases_ dissOlvèd in the Water;
_
Animals
_
cannot live without oxygen…— We extract :the. oxygen that,
we breathe in with
airinto our lungs, and .itis’ carriè‘d