492 
GEOLOGY: E. BLACKWELDER 
in several ways. Much of it is absorbed by plants and thus vicari- 
ously by animals, but returns again to the soil after the death of the 
organism, if not before. A very large part either immediately or even- 
tually joins the streams and finds its way to the ocean, suffering on the 
way certain minor losses which may be passed over here. 
Of the vast quantities of dissolved mineral matter delivered to the 
ocean annually by streams, it is estimated that nearly | of 1% (0.45%) 
consists of phosphoric acid. Using the best available figures for the 
amount of water reaching the ocean, we may calculate that if the phos- 
phatic material in the form of tricalcium phosphate were loaded into 
standard railroad cars it would fill a train stretching continuously from 
New York to Seattle and would be from 7 to 12 times as great as the 
world ^s total production of phosphate rock in 1911. Nevertheless so 
great is the volume of the oceans, and so vast the area of their floors, 
that if all of this material were converted into phosphatic minerals and 
deposited uniformly over the bottom of the sea, it would serve to form 
annually a layer less than i mm. thick. Of the phosphorus poured 
into the sea, so large a proportion is utilized by living things that the 
net working balance dissolved in oceanic water at present averages less 
than 0.005%, expressed as P2O5, or about \% of the salts dissolved. 
This seemingly represents the most diffuse state reached by phosphorus 
in the course of its complex migrations. Its subsequent transforma- 
tions, now to be described, generally tend toward ever greater con- 
centration almost until the cycle is closed upon itself. 
Soluble phosphates are absorbed by the myriads of oceanic plants. 
In some measure they become chemically linked in organic compounds 
but for the most part they probably remain as salts or ions. Living 
diatoms and other algae contain in both of these states tV to to% of 
P2O5. These organic substances containing phosphorus are devoured 
by an all but infinite variety of aquatic animals, each of which is in its 
turn liable to a similar fate. This endless process of devouring is recog- 
nized even in the ancient Chinese proverb to the effect that ''the big 
fish eat the little fish, and the little fish eat the shrimp, and the shrimps 
eat the mud." In the individual animal, the phosphorus forms a con- 
stituent of its tissues, cells, liquids, and in some groups also its teeth, 
bones, shells and other hard parts. 
There are at least two ways in which the phosphorus may escape 
from this oceanic cycle. The organisms of the sea may be eaten by 
land animals, chief of which are the birds, or the phosphorus may be 
fixed among the soHd deposits on the sea bottom and eventually buried 
beneath the accumulating sediments. The second of these processes 
will be considered first. 
