54 REVIEWS. 



by some peculiar characters of the coniferous fossils found in the valley of the 

 Tweed, for they have few and very slight appearances of concentric rings, which 

 arise from interruptions of growth, consequent on changes of temperature. 



M The scenery of these primaeval lands, though not glowing with beauty nor 

 radiant with light, has its charms, and arrests attention by the strangeness and vast 

 proportions of its vegetation. The summits of the hills and slopes of the mountains 

 were adorned by the picturesque forms of the lofty araucarias and other cone- 

 bearing trees ; on the extended swampy plains, dense forests of gigantic club- 

 mosses flourished, their huge arms flung wildly out, and covered with scaly leaves, 

 and terminated with cones; fluted trees stood erect on widely-spreading roots, 

 their long narrow leaves forming a series of drooping curves rising from the summit 

 and sides of the stem, and giving to the scene sepulchral solemnity ; tall reeds 

 sprung upward, straight as the mast of a vessel, with slender leaves or branches in 

 whorls around the stem. The foliage of the whole was sombre, but somewhat 

 relieved by the brighter green herbaceous ferns which grew in the shade, and by the 

 graceful tree ferns crowned with overarching fronds. No warm-blooded creature 

 then • walked the earth' — no beast roamed through the forest — no bird was there 

 with its gay plumage and sportive song ; only a few reptiles crawled in the swamps, 

 and an insect here and there fluttered on the wing ; yet the thoughtful mind, con- 

 necting this scene with the distant future, feels deeply interested with its aspect and 

 bearings ; for here the all-wise Creator, who adjusts the working of physical laws 

 to the attainment of moral purposes, caused the vegetative powers of nature to put 

 forth their strength, to make provision for the future wants of the intellectual and 

 moral beings who were to people the world. 



M It now remains for us to attempt to explain the chemical changes which the en- 

 tombed vegetable mass has undergone in its conversion into coal. 



" Coal is formed of the same elements as wood, but in different proportions. 

 Leaving out unessential materials, wood is composed of oxygen and hydrogen 

 gases united with about an equal quantity of carbon. Oak, for example, contains 

 49.432 parts of carbon, 44.499 of oxygen, and 6.069 of hydrogen. Now, when 

 wood is immersed in water, a change commences, which Liebig calls mouldering, 

 and which is different from the decay which results when air is freely admitted ; 

 oxygen and hydrogen are given off, in combination with smaller quantities of 

 carbon ; the hydrogen and carbon forming carburetted hydrogen, the fire-damp of 

 miners; and the oxygen and carbon forming carbonic acid, the choke-damp of 

 miners. Trees submerged in bogs are undergoing this change ; and, hence, the 

 swamps bordering the Mississippi are constantly emitting carburetted hydrogen, 

 especially wherever the ground is dug into. Bog-wood, therefore, contains a larger 

 proportion of carbon than wood does, its composition being 57.0 of carbon, 37.5 

 of oxygen, and 5.9 of hydrogen. When the mouldering process has gone on for a 

 longer period, lignite, such as is found in the tertiary beds, is formed, in which the 

 carbon is further increased, the composition being 58.56 of carbon, 26.85 of oxygen, 

 and 5.95 of hydrogen. As we go backward in time, the disproportion becomes 

 greater, for the rich bituminous Bensham coal, belonging to the Newcastle coal- 

 measures, consists of 86.44 of carbon, and only of 5.67 of oxygen, and 5.74 of 

 hydrogen. And in anthracite, where the series of changes is nearly completed, the 

 oxygen and hydrogen have all but disappeared, and the result is nearly pure carbon. 



44 Here a practical hint may be given. Some persons, especially those living in 

 the country, expose coals to rain, in the belief that their quality will be thereby 

 improved ; but exposure to moisture hastens on the decay of coal — it cannot, 

 indeed, be stored in too dry a situation. For steam-vessels, dry storage is of great 

 importance, because access of moisture, besides wasting coal, may cause spon- 

 taneous combustion, when sulphuret of iron is in combination with the coal. 



"The mouldering process is still going on in coal-fields, for to this is owing the 

 evolution of carburetted hydrogen, the dreadful enemy to miners ; and yet this 

 destructive element, when rightly treated, ministers to our wants, cooking our food, 

 and lighting our villages and towns. Bearing in mind what has already been 

 achieved in controlling and directing the powers of steam and of the electric fluid, 

 it may be hoped that science, impelled onward by humanity, will ultimately be able 

 to bring the carburetted hydrogen from the mine, where it spreads misery and 



