A step farther back in geological history we reach the period of the latest formations of lignite or brown coal. This coal is first found in the strata of the glacial period, or first period in the age of Man. But it is found there in an undeveloped state. The woody fibre has not yet undergone the complete transformation into coal. The trunks and branches of trees have indeed become softened to the consistence of soap, but they still retain their natural color. Going back, however, to the strata of the Miocene or second period of the Tertiary age or age of Mammals, we find that this wood has become black, though it has not yet hardened. But when we reach the upper cretaceous or last period of the age of Reptiles, the transformation into coal has become complete. The woody fibre is now black, hard, and compact, though it may still be easily disaggregated by atmospheric action, and we have the true lignite, so called because of its apparent woody structure. The next step takes us back to the bituminous coal of the Carboniferous age, the character and consistency of which has already been noted, and finally we reach the complete development in anthracite. It is, however, the opinion of the best geologists that the bituminous and anthracite coals are of the same age, and were originally of the same formation and character. That is, they were all bituminous; but during the violent contortions and upheavals of the earth’s crust at the time of the Appalachian revolution at the close of the Carboniferous age, the bituminous coals involved in that disturbance were changed by heat, pressure, and motion, and the consequent expulsion of volatile matter, from bituminous to anthracite. Cannel coal is a variety of bituminous coal, burning with great freedom, the flame of which affords considerable light. It was called “candle coal” by the English people who first used it, as it often served as a substitute for that household necessity. But the name soon became corrupted to “cannel,” and has so remained. It is duller and more compact than the ordinary bituminous coal, and it can be wrought in a lathe and polished. A certain variety of it, found in the lower oölitic strata of Yorkshire in England, is manufactured into a kind of jewelry, well known by its popular name of _jet_. CHAPTER III. WHEN COAL WAS FORMED. It becomes of interest now to examine briefly into the causes and process of the transformation from vegetable substance into coal, to note the character of the vegetation which went to make up the coal beds, and to glance at the animal life of the period.