Part 80. Fuel, whether as a source of heat or of power, being indispensable to the carrying on of almost every industry, and being also a necessity for steam-transportation, for the heating of buildings, and for cooking, it is plain that civilization could not have developed as it has, nor could it possibly go on, without this source of heat,

Anything which burns readily in the air will serve as fuel; and, indeed, various sorts of refuse are thus utilized: for example, wheat straw is made to run steam threshing-machines, and the crushed stalks of sugar-cane are used in the boiling of the juice. But, in general, wood, peat, and coal, and their products, charcoal, coke, and illuminating gas, are the fuels most extensively used.

Peat - Plant Fuels

Peat consists of the more or less carbonized and compacted deposits of vegetable substances which accumulate in bogs and marshes, and, in the presence of water, slowly decompose. Peat-bogs form chiefly in northern countries. Near the surface they consist largely of moss like that shown in Fig. 227 with which, however, a number of other plants are found growing. In the deeper layers that have been buried for a long period of time, the material is so transformed as to be like a soft, brown coal. In regions where wood is scarce peat is highly valued as a fuel. It is commonly more bulky than wood, and has from 5 to 15 times as much ash. Its heating power is about the same.

- Plant Fuels

Illuminating-gas is made by subjecting coal or wood to a high temperature in a retort, and collecting and purifying the gas given off. For obvious reasons coal-gas has proved to be a most convenient fuel especially adapted for household use in large cities.

The study of fuels leads one to think not only of the forests of to-day and of bog-plants that lived perhaps hundreds of years ago, but in imagination one is led back to strange forests which disappeared from the earth many thousands of years ago and became turned to stone. Therefore, if we ask ourselves, Whence comes this material that men burn to get heat and power? the answer is, From the bodies of plants, some of which lived ages before the coming of mankind. And if we further ask, Whence comes the energy which all these plants have stored in their bodies, and left for us to set free? students of nature tell us, From the sun. That is to say, plants with foliage are the sunbeam-traps of our planet, and except for their marvelous ability to lock the energy of sunshine into the material of food and fuel, the life of the world as we know it would be impossible. How plants are able thus to store up sunshine, and why they do it, are questions to be answered only by the study of their processes of life.