240 WARREN J. MEAD 
In the present paper the redistribution of the elements of the origi- 
nal crystalline rock will be taken up from a purely chemical stand- 
point. It will be the purpose to determine in what proportions the 
various sediments should be combined to yield an average compo- 
sition most nearly like that of the original rocks from which they 
were derived, and to point out reasons for discrepancies which may 
develop. 
We may look upon the table given on page 239 as an equation 
which may be written as follows: 
“/ Shales 
Sandstone 
Limestone 
Original crystalline rock + Redistribution agencies= ( Vein-filling materials 
Cementing materials 
Salts of the sea 
Residual matter 
If the several end-products making up the right-hand side of the 
equation could all be taken into account in proportion to their abun- 
dance, it is evident that the elements of the original rock would all 
be accounted for unless some minor factor has been overlooked. Of 
these end-products fair average chemical analyses are available for 
shales, sandstone, and limestone, and also for the salts of the sea. 
Of the vein-filling material very little is known in regard to abun- 
dance, and an average chemical analysis is impossible. Better, but 
still poor, results may be obtained from the residual materials. ‘The 
cementing material is included in the analyses of the mechanical 
sediments. ‘The sedimentary rocks form the major part of the mass 
of the secondary material, the other end-products being only a small 
percentage of the total mass; hence the proper combination of their 
analyses should approximate the original rocks—i.e., the left-hand 
side of the equation—even if the less important end-products be not 
counted, though their omission will cause certain discrepancies. ‘Thus 
we may expect to find a deficiency of iron, owing to its segregation in 
iron formations and iron-ore deposits, which are not included in the 
analyses of the sediments. We may expect to find a deficiency of 
sodium, owing to the large amount of that element in solution in the 
sea. 
Our purpose, then, is to ascertain in what proportions the sand- 
stones, shales, and limestones should be combined to give the best 
