328 JESSE E, HYDE 
at intervals, when it would accumulate to a considerable thickness— 
several inches— in a short time. At these intervals it might bury 
a tongue of the plant mat which had spread out over preceding 
sands, but was often insufficient to cover the whole, and received 
a check, possibly from the plants themselves, that held it back of 
the main bed. As soon as an accumulation of sand buried the 
plants entirely at any one point, growth recommenced at the new 
margin. That there were frequently a number of such attacks by 
the sand which only covered thin extensions of the plant bed, is 
shown by the presence not infrequently of three or four or more 
beds of sandstone interbedded at the side of the coal, but not 
encroaching to any extent on its main body: Had the accumula- 
tion of the coal mud been due to deposition from suspension, it- 
seems highly improbable that the sandstone incursions would have 
respected the unity of the deposit to any such degree. 
The coal, too, in the main bodies and in most of the stringers 
is remarkably pure (ocular inspection only). Occasionally a thin 
clay parting is to be observed in undisturbed portions which is 
undoubtedly original in the coal, but these are so far absent, 
although to be expected in such accumulations as to negative 
further the suspension theory for the origin of the coal. 
There is, however, no suggestion of a basal clay beneath the 
many thin stringers of coal which are found in the sandstone. 
Nor are there any of the characteristics of a basal clay or fire clay 
to be observed in the soft gray shale which underlies the coal 
deposits where they are thickest and without sandstone lenses, 
although these have usually been considered characteristic of 
growth of vegetation in place. However, the marginal swamp 
theory and the accumulation of the vegetable mud by growth in 
position is apparently a much more satisfactory explanation of the 
deposit as a whole than the flotation theory and is believed to be 
the correct one in this case. To say the least, the whole suggests 
very strongly that it may be possible for coal to be formed by 
growth in position, the time-honored conception of coal formation, 
without the development of an underclay full of root impressions, 
the presence of which has always been one of the chief facts in 
evidence to support this conception. 
