REDISTRIBUTION OF TITANIUM. 975 



original magnetite of many rocks is strongly titaniferous, and because of 

 its abundance may be the chief home of titanium. 



Titanium forms 0.65 per cent of 78 shales; 0.33 per cent of 624 sand- 

 stones, and 0.07 per cent of 843 limestones. It thus appears that as com- 

 pared with the original rocks the amount of titanium is somewhat increased 

 in the shales, is reduced to a little more than one-half in the sandstones, 

 and is less than one-eig-hth in the limestones. If one were to estimate the 

 amount of titanium in the original igneous rocks by the amount in the 

 sedimentary rocks we would have the following equation: 



.65x.65-t-.33x.30+.07x.05=.525. 



This accords very well with the actual amount as estimated by analyses 

 in the original igneous rocks, 0.55 to 0.60 per cent. The minerals produced 

 by metamorphism are the same as those of the original rocks. The details 

 of the transformations with reference to the different zones and belts of 

 metamorphism have not been worked out. Titanium minerals have been 

 especially observed in the metamorphosed pelites and psephites, and to this 

 observation the analyses above given correspond. 



PHOSPHORUS. 



According to Clarke's estimate of 1891 phosphorus forms 0.09 per cent 

 of the outer 10 miles of the crust of the earth, including the original rocks, 

 hydrosphere, and atmosphere. All of it is in the lithosphere, of which it 

 composes 0.10 per cent. In his estimate of 1900 Clarke reduces this amount 

 to 0.09 per cent. 



Phosphorus is thus twelfth in the scale of abundance, ranking next to 

 carbon, an element of vastly greater importance. Reckoned as an oxide 

 Clarke's estimates of 1891 and 1900 are both 0.22 per cent." This gives 

 phosphorus oxide eleventh place in the table of oxides. In the original 

 rocks phosphorus is known to occur only in the mineral apatite, of which 

 it composes 18.47 per cent. This mineral, while usually subordinate in 

 amount, is very widespread. In the meteorites phosphorus is found in 

 schreibersite (FeNiCoI 3 P). (See p. 946.) The amount of P 2 5 hi 78 shales 

 is 0.17 per cent; in 624 sandstones 0.07 per cent; in 345 limestones not 

 used for building purposes is 0.04 per cent, while in 498 limestones used for 

 building purposes it is 0.42 per cent. 6 



« Clarke, cit., Bull. 78, p. 39; Bull. 168, p. 15. & Clarke, cit., Bull. 168, p. 14. 



