316 The American Geologist. ba 
metamorphism. Under that part of the table called “Results of 
Metamorphism” the percentages of the constitutents are given into 
which the sediments break up in the production of the metamorphic 
mineral. 
The latter is the only one of them remaining in the strata, the 
others escaping as gases, and thus its percentage indicates the amount 
of shrinkage. 
On being set free the gases expand to many times the original 
volume of the sediments, the numbers in the table being the volume 
to which they expand at o degrees centigrade and 760 millimeters pres- 
sure, the unit being the original volume of sediments. In computing 
the volumes of the metamorphosed strata, the porosity factor, being a 
variable quantity, has not been included, but nevertheless it is seen 
that in all cases the shrinkage in volume is greater that the shrinkage 
in weight. 
Since to use this table it may sometimes have to be supplemented, the 
method of compution is given below: 
Grossularite, Cag Ale(SiO4)3 
S$i0O2 40, AleOg 27°7, CaO 37°3 per cent. 
Silica, SiOz, mol. wt. 60° 
Kaolinite, HaAleSiea09, mol. wt. 258'8. 
2H20=36, Al2Og=102°8, 2S8i02=—120. 
Calcite, CaCOg, mol. wt. 100. 
CaO=56, COo—44. 
Using grossularite as a basis of compution. 
ys ake =57°2; amt. of kaolinite required by 100 parts of 
grossularite. 
Bi 2 eee =26.5; amt. of silica brought in by kaolinite 
D58'Bia ray! Mees 8 y ; 
57° 2 x Bb =8'0; amt. of water brought in by kaolinite. 
258'8 g 
40 — 26°5=13°5; amt. of free silica required by 100 parts of gros- 
sularite. 
‘ 100 ; : ; 
37°3 x 56 =66°6; amt. of calcite required by 100 parts ofgrossularite. 
ae. 44 ae ; ' 
66°6 x 56.293; amt. of carbon dioxide brought in by calcite. 
Thus: — 
57°2 Kaolinite  ) { 100° Grossularite. 
13°5 Quartz | | 8.0 Water. 
66°6 Calcite t , 29.3 Carbon dioxide. 
137°3 Sediments | igs Nes 7 ile 
Bringing this to a basis in which the amount of sediments shall form 
the unit gives the following figures: — 
100 parts of sediments consisting of 41.7 kaolinite, 9°8 quartz and 
48°5 calcite yield 72'°8 parts of grossularite, 21°4 carbon dioxide and 
5°8 of water as shown in the table. 
