Ill Tk« Amcr/rrn) (»Vo/, - .)nn<- - 
anthracite; and at first glance might readily be mistaken for 
it. It is. hovever, much softer and more brittle, Thepereent- 
age of ash is very much less than in any other Iowa or 
Missouri coals, .-mil in other respects it may be regarded as the 
host grade found in either of the two states mentioned. 
These factors are suggestive that in the formation of certain 
coals, and especially those having the phys tiaracters 
anthracite, the original conditions of deposition may have 
played a more important part than has been generally suppos 
ami that the origin of the materials was quite different from 
that formauyof the ordinary bituminous kinds. 
The implication that in th< - I anthracite the coal- 
forming materials were almost entirely changed about the 
time of, or soon after, deposition, because of the longer i s 
posure to atmospheric influences than in the case of the bitu- 
minous varieties, practically precludes any subsequent alter- 
ations after the plant remains have been covered up by sedi- 
ments. Few elastic rocks are not porous enough to permit of 
a more or Less ready circulation of underground water. M 
over, crustal deformation, no matter how small it - g 
rise bo changes of some sort in the character of the beds 
fected, Ifineralogieal alterations in the mineral constituents 
are thus ever going on in the rocks. Indeed, the whole min- 
eralogical composition and structure of stony aggregates are 
being modified continually ; in some places slowly, in others 
more rapidly, according to the attending circumstances. Tin- 
ever changing physical conditions invariably set up continu- 
ous molecular shiftings in every roek.no matter what its com- 
position or what its relations. 
It has been said that the changes undergone by rock n -- - 
have been occasioned by the natural tendencies of minerals to 
assume combinations more stable from those less stable. Rut 
the statement has not carried with it the full import and 
meaning that it should: for in any particular case, while 
there is an attempt towards adjustment to satisfy a certain 
set of conditions, the conditions themselves are continually 
changing, sometimes in one direction, sometimes in another. 
In the production of these alterations in rock masses time 
does not necessarily enter as a factor, although ordinarily the 
