A 
C. 8. Garnett—Alteration of Shales in Derbyshire. 477 
If ozone, derived as suggested, was responsible for any of the 
phenomena noted, perhaps it might be expected that some compound 
of manganese would be found in the altered zone, and such is the 
case; clayey matter heavily impregnated with brown oxide of 
manganese is to be found in some quantity among the altered beds. 
Thus, whilst the general phenomena are those of combustion of 
spontaneous origin such as may arise from the oxidation of pyrites, 
some of the observations described would perhaps seem to be rather 
the effect of active percolating water. The actual shales hereabouts 
do not contain either pyrites or the products of its oxidation in 
any appreciable quantity, and the ferric oxide in the altered shale 
is somewhat uniformally distributed in the latter and does not 
exceed 4%. Thus, if combustion spontaneously arose in such 
manner, it would seem to have probably done so at a place in 
closer contact with the limestone veins, and as at the place of 
exposure the altered beds overlie normal shale at probably about 
30 feet above the limestone, the fire would seem te have spread 
horizontally from such place, which, as the dip is somewhat steep, 
would be not far distant but would probably involve its passage for 
a short distance under some beds of shale, leaving them normal 
and unaltered. The occurrence cf brown oxide of manganese in 
some quantity in the position would be a singular coincidence if 
simple combustion was the, or the only, cause of the phenomena. 
Also, with regard to the phosphatic nodules, to account for the 
condition of the completely altered examples would seem to require 
some agency other than simple combustion, namely, at least a dilute 
sulphuric acid solution, and all such examples were found at an 
obvious water course in the strata at a low horizon in the altered 
beds. 
