woody portion of the plant, and the pyropissite (tar coal) to the resinous matter it contained.

The tar coal, or pyropissite, forms bands or alternating strata with the fire coal, or is scattered through it in irregular masses. Prof. von Fritsch argues that the trees could not have grown at the locality of the brown coal deposit, for had that been the case there would have been an intimate mingling of the two materials both derived from the same trees, as is the case in other localities, but that they have been brought in from elsewhere, and the sorting action of the water has separated the tar coal from the fire coal by reason of their different specific gravities when brought to their place of deposit.

Coal is produced by the chemical alteration of vegetable matter in the presence of water. And the processes by which the beds of coal were formed are in steady and gradual operation around us today.

These are:

• 1. The decomposition of the vegetable matter: a. In contact with air. b. Out of contact with air.
• 2. The deposition of the decomposed materials: a. At the place of its origin. b. At other localities.
• 3. The subsequent alteration of the deposits by slow or more rapid metamorphism.

a. In contact with air.—Vegetable matter, which is composed principally of carbon, hydrogen, and oxygen, when exposed to the action of the air undergoes change in two ways. It is partly oxidized by the air, or decays, and partly decomposed. In the process of oxidation or decay there is a loss of carbon as carbonic acid, and hydrogen as water, and the final resultant would be a pure carbon. This is believed by some to be the method of formation of the mineral charcoal which is found between the layers of many bituminous coals, and which consists of nearly pure carbon. Where the atmosphere is sufficiently moist, this final carbonization does not occur, but the process takes more nearly the form of mouldering.

b. Out of contact with air.—The change of vegetable matter out