Universal Source of Heat.
Dr. Percy, in his very able Treatise on Metallurgy, gives an explanation of the principle that the sun is really the source of the heat-producing power of all fuel; and we are inevitably reminded of the question with which George Stephenson puzzled Buckland. “Now, Buckland,” said Stephenson, as they were looking at a train in motion, “can you tell me what is the power that is driving that train?” “Well,” said the other, “I suppose it is one of your big engines.” “But what drives the engine?” “Oh! very likely a canny Newcastle driver.” “What do you say to the light of the sun?” “How can that be?” asked the Doctor. “It is nothing else,” said the engineer: “it is light bottled up in the earth for tens of thousands of years; light, absorbed by plants and vegetables, being necessary for the condensation of carbon during the process of their growth, if it be not carbon in another form,—and now, after being buried in the earth for long ages in fields of coal, that latent light is again brought forth and liberated, made to work, as in that locomotive, for great human purposes.” Dr. Percy explains the process by which this light or heat is stored, and discusses the question of fuel in all its forms and branches. We find under this head, inter multa alia, an account of the manufacture of the peat-bricks in South Bavaria, which have for some years past been used for the boilers of locomotives; again, an explanation of the failure of Mr. Vignoles’s process of manufacturing iron in Ireland by means of peat charcoal, in consequence of the value of the raw material so much exceeding his estimate; besides an elaborate discussion on that litigated question so differently judged by different tribunals, and still undecided—“What is or is not coal?”
Inequalities of the Earth’s Surface.
The earth is a spherical body, or, more correctly, an elliptic spheroid. Its surface, therefore, may be considered equidistant from its centre point within, and of uniform curvature. This is so as regards the ocean, which is
“Unchangeable save to its wild waves’ play;”
but the surface of the land is very diversified. In parts it is spread out into plains; in others, into easy undulations. Here and there it rises into hills, with valleys and extensive basins between them; while at places chains of mountains appear at varying altitudes, some of which penetrate the clouds.
Although the irregularities of the small portion of land which we can see at one view seem very considerable, and more especially the largest mountains, yet these protuberances are insignificant when compared to the magnitude of the earth itself.
Mount Everest, in Nepaul, is the loftiest point of the Himalaya chain, and the highest mountain in the world. It rises 29,002 feet—equal to 5·49 miles,—above the level of the sea. This height is only
| ( | 7912·40 ———— 5·49 | ) | 1 ———— 1441 |
| ( | 1441 —— 12 | = | ) |