40 
FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
some are very rare, occurring only in small amounts, while others 
are abundant. The element oxygen alone is estimated to make up 
49.78%, or practically one-half of all known terrestrial matter, 
while oxygen and silicon together make three-fourths (75.86%). 
The nine most abundant elements, oxygen, silicon, aluminum, iron, 
calcium, magnesium, sodium, potassium, and hydrogen, make up 
98.3%. The twenty most abundant elements make up 99.52%, the 
remaining sixty elements combined constituting only .48%. These 
estimates are made by F. W. Clarke, of the United States Geological 
Survey and are based on a calculation of the constituents of the air 
and the ocean, and of the crust of the earth to a depth of ten miles. 
The materials of the interior of the earth at a depth greater than ten 
miles are too imperfectly known to be included in the estimate. 
The following is the list of the twenty most abundant elements 
including the estimate of the amount of each in the crust of the 
earth as given by Professor Clarke.* 
Average composition of lithosphere, ocean, and atmosphere. 
Lithosphere 
Ocean 
Average, includ¬ 
(93 per cent.) 
(7 per cent.) 
ing Nitrogen. 
Oxygen . 
47.07 
85.79 
49.78 
Silicon . 
28.06 
26.08 
Aluminum . 
7.90 
7.34 
Tron . 
4.43 
4.11 
Calcium .. 
3.44 
.05 
3.19 
Magnesium . 
2.40 
.14 
2.24 
Sodium . 
2.43 
1.14 
2.33 
Potassium . 
2.45 
.04 
2.28 
Hydrogen . 
.22 
10.67 
.95 
Titanium . 
.40 
.37 
Carbon . 
.20 
.002 
.19 
Chlo r ine . 
.07 
2.07 
.21 
Rrnminfi . 
.008 
Phosphorus . .. 
.11 
.11 
Sulphur . 
.11 
.09 
.11 
Parinm . 
.09 
.09 
Mnnp'anpsfi . 
.07 
.07 
Strontium . 
.03 
.03 
Nitro^pn 
.02 
pinimino . 
.02 
.02 
All other elements. 
.50 
.48 
100.00 
100.00 
100.00 
*The Data of Geochemistry, Bull. 330, U. S. Geol. Survey, p. 32, 1908. 
