764 



DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



Lave been taken direetly from Clarke's work and all three sets are noted in the 

 following table: 



An inspection of the table makes it clear that the total of the ' combined 

 water,' carbon dioxide, carbon and carbonaceous matter, sulphur and chlorine in 

 the stratified rocks exposed in any geosynclinal prism must represent at least six 



Table LIIL — Volatile matter in sediments. 



843 624 116 



limestones sandstones argillites 



H,0— -26% -29% 1-25% 



H" 2 0+ -73* 1-41 3-71 



C0 2 38-03 2-64 2-45 



C (including: carbonaceous matter) ? ? -81 



S -11 -03 -25 



CI -01 trace trace 



Total 39-14 4-37 8-47 



* Includes organic matter. 



per cent of the whole mass. It is highly probable that this minimum amount 

 of volatile matter has similarly characterized such a series ever since the period 

 in which the series was deposited. 



No petrographer needs to be reminded that none of the commoner types of 

 igneous rock contains anything like six per cent of original volatile matter. 

 Nevertheless it is instructive to survey the facts actually visible in quantitative 

 analyses of the igneous rocks. Water is the only volatile substance determined 

 in igneous-rock analyses often enough to afford nearly reliable world-averages. 

 From Osann's compilation the writer has deduced the aver ge of H 2 - and 

 H 2 + for each of the following groups : 48 granites, 47 diorites, 12 gabbros, 24 

 basalts, 5 augite andesites and 11 rhyolites (Table LIV). 



Table LIV. — Water in igneous rocks. 



H 2 0— H 2 0+ 



Granite -17% -64% 



Diorite -19 1-20 



Gabbro -2« 1-35 



Basalt -73 1-03 



Augite andesite -40 1-48 



Ehyolite -30 1-23 



Clarke's averages for the volatile substances occurring in igneous rocks 

 which have been analyzed according to approved methods are : 



H 2 0— .40% 



H 2 0+ 1-46 



CO a .52 



S .11 



CI .07 



V .02 



Much of the combined water, probably all of the hygroscopic water, and 

 some of the carbon dioxide of these analyzed igneous rocks are due to alteration 



