We should not neglect to remark, however, that the word gein has been employed by some writers in the sense in which we use humus, viz.: to denote the brown or black products of the decomposition of vegetable matters.
It is scarcely to be doubted that other organic compounds exist in peat. As yet, however, we have no knowledge of any other ingredients, while it appears certain that those we have described are its chief constituents, and give it its peculiar properties. With regard to them it must nevertheless be admitted, that our chemical knowledge is not entirely satisfactory, and new investigations are urgently demanded to supply the deficiencies of the researches so ably made by Mulder, more than twenty years ago.
Elementary Composition of Peat.
After this brief notice of those organic compounds that have been recognized in or produced from peat, we may give attention to the elementary composition of peat itself.
Like that of the vegetation from which it originates, the organic part of peat consists of Carbon, Hydrogen, Oxygen and Nitrogen. In the subjoined table are given the proportions of these elements as found in the combustible part of sphagnum, of several kinds of wood, and in that of a number of peats in various stages of ripeness. They are arranged in the order of their content of carbon.
| Analyst. | Carbon. | Hydrogen. | Oxygen. | Nitrogen. | |
| 1—Sphagnum, undecomposed | Websky | 49.88 | 6.54 | 42.42 | 1.16 |
| 2—Peach wood, undecomposed | Chevandier | 49.90 | 6.10 | 43.10 | 0.90 |
| 3—Poplar wood, undecomposed | Chevandier | 50.30 | 6.30 | 42.40 | 1.00 |
| 4—Oak wood, undecomposed | Chevandier | 50.60 | 6.00 | 42.10 | 1.30 |
| 5—Peat, porous, light-brown, sphagnous | Websky | 50.86 | 5.80 | 42.57 | 0.77 |
| 6—Peat, porous, red-brown | Jæckel | 53.51 | 5.90 | 40.59 | |
| 7—Peat, heavy, brown | Jæckel | 56.43 | 5.32 | 38.25 | |
| 8—Peat, dark red-brown, well decomposed | Websky | 59.47 | 6.52 | 31.51 | 2.51 |
| 9—Peat, black, very dense and hard | Websky | 59.70 | 5.70 | 33.04 | 1.56 |
| 10—Peat, black, heavy, best quality for fuel | Websky | 59.71 | 5.27 | 32.07 | 2.59 |
| 11—Peat, brown, heavy, best quality for fuel | Websky | 62.54 | 6.81 | 29.24 | 1.41 |
From this table it is seen that sphagnum, and the wood of our forest trees are very similar in composition, though not identical. Further, it is seen from analyses 1 and 5, that in the first stages of the conversion of sphagnum into peat—which are marked by a change of color, but in which the form of the sphagnum is to a considerable extent preserved—but little alteration occurs in ultimate composition; about one per cent. of carbon being gained, and one of hydrogen lost. We notice in running down the columns that as the peat becomes heavier and darker in color, it also becomes richer in carbon and poorer in oxygen. Hydrogen varies but slightly.
As a general statement we may say that the ripest and heaviest peat contains 10 or 12 per cent. more carbon and 10 or 12 per cent. less oxygen than the vegetable matter from which it is produced; while between the unaltered vegetation and the last stage of humification, the peat runs through an indefinite number of intermediate stages.
Nitrogen is variable, but, in general, the older peats contain the most. To this topic we shall shortly recur, and now pass on to notice—
The ultimate composition of the compounds of which peat consists.