360 



PALEOZOIC TIME. 



covered regions beyond the Coal-measure limits. But yet it was an 

 era in which the changes for the most part went forward with so ex- 

 treme slowness, and with such prevailing quiet, that, if man had been 

 living then, he would not have suspected their progress, unless he had 

 records of some thousands of years past to consult. According to the 

 reading of the records, it was a time of great forests and jungles, and 

 of magnificent foliage, but of few or inconspicuous flowers ; of Acro= 

 gens and Gymnosperms, with no Angiosperms ; of marsh-loving In= 

 sects, Myriapods, and Scorpions, as well as Crustaceans and Worms, 

 representatives of all the classes of Articulates, but not the higher 

 Insects, that live among flowers ; of the last of the Trilobites, and 

 the passing climax of the Brachiopods and Crinoids ; of Ganoids and 

 Sharks, but no Teliosts or Osseous Fishes, the kinds that make up 

 the greater part of modern tribes ; of Amphibians and some inferior 

 species of True Reptiles, but no Birds or Mammals ; and therefore 

 there was no music in the groves, save that of Insect life and the 

 croaking Batrachian. Thus far had the world progressed, by the close 

 of the Carboniferous period. 



The special history of the Coal-period of Europe and Britain might 

 be followed out, as has been done for North America. But the de- 

 tails would illustrate no new principles, and would be more appropriate 

 in a general treatise than in a text-book. More facts are to be ascer- 

 tained, before their history will be as clearly deciphered. 



4. Formation of Mineral Coal. — From the analyses on page 316, 

 it is seen (1) that mineral coal consists chiefly of carbon ; (2) that, 

 also, hydrogen and oxygen are always present ; (3) that Anthracite 

 contains usually 2 to 5 per cent, of oxygen and hydrogen ; and the 

 Bituminous coals often 12 per cent, in weight of oxygen, and 4 to 6 

 of hydrogen ; while Brown Coal, the bituminous coal of later forma- 

 tions (which ordinarily gives a brownish -black powder), contains 20 

 per cent, or more of oxygen, with 5 or 6 of hydrogen. 



Mineral coal, therefore, is not carbon, but a compound, or a mixture 

 of two or more compounds, of carbon, hydrogen, and oxygen, asso- 

 ciated probably with some free carbon in anthracite, and possibly in 

 some or all bituminous coal. In this view, coals are mainly oxydized 

 hydrocarbons, or mixtures of them. As stated on page 314, they are 

 scarcely acted on by ether or benzine, and hence contain no mineral 

 oil, or only a trace of any soluble hydrocarbon ; but, at a high temper- 

 ature, hydrocarbons (compounds of hydrogen and carbon) are given 

 out, in the forms of either mineral oil, tar, or gas, 



The coal, as has been shown, is derived from the alteration of vege- 

 table material. This vegetable material is (a) woody fibre ; (b) cel- 

 lular tissue ; (c) bark ; (d) spores of Lycopods (Lepidodendrids, etc.) ; 



