360 The American Geologist. December, 1894 
layers of sediment transported and stratified by or under water, 
the original shape was probably more or less lenticular, being 
thicker and coarser shoreward, and thinner and finer-grained 
seaward. And since, in the area in which these binders are 
now confined, their composition, texture, etc., hardly seem to 
vary at all, we naturally ask, How large an area did the now 
denuded, binder-divided coal seam once upon a time cover?; 
the only answer is, simply immense! Can we suppose any- 
thing short of scores of times larger than at the present day! 
What do the facts seem to suggest? 
(a) Having to deal with a comparatively very thin sheet of 
what looks like an originally almost impalpable powder or 
the finest slime or mud, distributed in a marvelously uniform 
manner, and covering an area almost continental in size, we 
wonder which of the known ways in which strata are formed 
best answers or explains the phenomena. Basing our argu- 
ment upon the supposition that the termination of the deposi- 
tion of the stratum of coal-forming vegetation upon which 
the lower sheet of shale rests, found that stratum lying prac- 
tically level as accumulated under water or on the bottom of 
a vast lake or inland sea, let us endeavor to imagine the wa- 
ters to be charged with fine particles of sediment, brought in 
from the mouth or mouths of immense rivers flowing in the 
then continental areas which furnished the sediments com- 
posing the coal-measures. The character of the shale binder 
points to a uniform mixture of sizes and kinds of particles, to 
an even or continuous supply of the same at the commence- 
ment of its falling to the bottom of the water, during all the 
period thus occupied in sedimentation, and up to the time the 
particles ceased to accumulate; practically no variation in 
strength or velocity of current of water supplying or parting 
with its muddy ingredients ; a rate of flow of water hardly 
perceptible ; a period of calm as regards wind and waves ; a 
depth of water absolutely the same all over the expanse or 
area of precipitation ; this implies perfect freedom from local 
currents and irregularities of bottom; no drifting logs or 
snags to scrape or plow up the bottom ; a time on land of no 
floods or droughts important enough to interfere with or 
break the continuity of the supply of mud transported. We 
have also to suppose that the rivers, deriving sediment by 
