170 Proceedings of the Koyal Society of Edinburgh. [Sess. 
aqueous extract, as given by Mr Steiger’s figures, is very near that of the 
sea-salts. I have therefore taken Dittmar’s analysis of sea-salts as a 
standard, and subtracted their equivalent, as measured by the chlorine in 
the unleached clay, from the analysis of the latter. A slight excess of S0 3 
remained, which I have also thrown out as representing gypsum. In short, 
from the general analysis I have withdrawn the water lost below 106°, the 
sea-salts, the calcium carbonate, and a little gypsum, and recalculated the 
remainder to 100 per cent. 
For comparison, I have combined the twenty-five analyses of the 
Challenger report into an average, from which similar subtractions, so far 
as they were needed, have been made. In this case only gypsum and 
calcium carbonate were rejectable. As for the combination, its value is not 
very great, because of the inequality shown by the individual analyses. 
Only in four of the latter were alkalies determined, and the mean of those 
four I have assumed to be representative of all. The ferrous oxide is even 
more doubtful, for it was only determined in one of Hornung’s analyses, and 
neglected in the others. Still, as will be seen in the subjoined table, the 
comparison is not without significance, and even if it is not perfect, it is 
better than none at all. 
REDUCED ANALYSES. 
Si0 2 . 
Composite 
Analysis. 
. 54-48 
Challenger 
Average. 
54-28 
Ti0 2 . 
. -98 
A1A • 
. 15-94 
16-41 
Cr 2 0 3 . 
. -012 
Fe 2 0 3 . 
. 8-66 
13-58 
FeO . 
. -84 
1-26 
NiO, CoO 
. -039 
. . . 
Mn0 2 . 
. 1-21 
1-62 
Mg(P . 
. 3-31 
1-76 
CaO . 
. 1-96 
•74 
SrO . 
. -056 
BaO . 
. -20 
k 2 o . 
. 2-85 
1-61 
Na 2 0 . 
. 2-05 
1-37 
v,o» • 
. -035 
As 2 0 3 . 
•001 
Mo0 3 . 
. trace 
PA • 
. -30 
•35 
CuO . 
. -024 
PbO . 
. -008 
ZnO . 
. -005 
h 2 o . 
. 7-04 
7-02 
100-000 
100-00 
