[42] Data recalculated, omitting ash. PROGRESS OF HUMIFICATION, AND FORMATION OF COAL. (MOISTURE AND ASH OMITTED FROM CALCULATIONS.) ========+==========+======================+============+ | | Oak Wood. | | | +------+--------+------+ Humin | |Cellulose.|Fresh.|Decayed.| | and | | | +--------+------+ Humic | | | | Light | Dark | Acid. | | | | Brown. |Brown.| | --------+----------+------+--------+------+------------| Carbon | 44.44 | 50.60| 53.60 | 56.20|49.4 to 59.7| Hydrogen| 6.17 | 6.00| 5.20 | 4.90| 2.5 “ 4.5| Oxygen | 49.38 | | | |35.8 “ 47.3| | | 43.40| 41.20 | 38.90| | Nitrogen| | | | | .3 “ 18.7| --------+----------+------+--------+------+------------+ ========+======================+================================ | Peat.[43] | Coals. |--------+-------------+--------+-----------+----------- | Brown | Black. | Lignite| Scotch | Penn’a |Surface.+------+------+ Brown | Splint |Anthracite. |(Ulmin.)|40 in.|80 in.| Coal. |Bituminous.| | | | |(Bovey).| | --------+--------+------+------+--------+-----------+----------- Carbon | 57.80 |62.00 |64.10 | 69.50 | 84.20 | 94.80 Hydrogen| 5.40 | 5.20 | 5.00 | 5.90 | 5.80 | 2.60 Oxygen | 36.00 |30.70 |26.80 | 24.00 | 8.80 | } | | | | | | } 2.60 Nitrogen| .80 | 2.10 | 4.10 | .60 | 1.20 | } +-------+--------+------+------+--------+-----------+----------- [43] Detmer, Landw. Versuchst., Vol. 14, 1871. The steady increase of carbon and nitrogen, together with a corresponding decrease of oxygen, are well illustrated in the analyses, especially in the strictly comparable series of peat samples from various depths. In this case there is also a steady decrease of hydrogen, and an increase of ash from 2.72% in the surface layer, to 9.16 at 80 inches depth. This increase is due in the main, of course, to the progressive volatilization of the organic matter in the forms of carbonic dioxid and marsh gas (methan, CH₄).