The combustion of _carbon_ takes place without the production of flame. The charcoal (or carbon in any other form) being heated to redness, enters directly into combination with the _oxygen_ of the surrounding air, and the carbonic acid gas, being invisible, passes away unobserved. But in the combustion of _hydrogen_ the heat developed is so intense as to render _the gas itself luminous_, just as iron may be heated to a red or white heat. 269. _What has become of the candle when it has been burnt?_ It has been resolved partly into _carbonic acid gas_ which, though unperceived, has diffused itself through the surrounding air; and partly into _water_, which escaped in the form of thin vapour. 270. _Has any part of the candle been consumed or lost?_ No; there is no such thing as "loss" in the operations of nature. Every particle of the candle, now invisible, exists either in the form of _gas_, _vapour_, or _water_, with, perhaps, a few solid particles that may be called _ashes_, but which are too minute to excite attention. [Verse: "I know that whatsoever God doeth, it shall be for ever: nothing can be put to it, nor anything taken from it; and God doeth it that men should fear before him."--ECCLES. III.] The economy of nature should teach us a very impressive lesson--_nothing is suffered to be wasted_, not even the slightest atom. As soon as any body has fulfilled its purpose in one state of being, it is passed on to another. The candle, existing no longer as a candle, is flying upon the wings of the air as _carbonic acid gas_, and as _water_. These probably find their way to the garden or the field, where the carbonic acid gas forms the _food of the plant_, and the water affords it a refreshing _drink_. And can it be supposed that the Almighty Being, who has thus economised the existence of the _material_ creation, should be less mindful of the immaterial _soul_ of man? There _is_ an eternity before us, the certainty of which is evidenced even by the laws of the material creation. CHAPTER XIV. 271. _What is coal?_ Coal is a "_vegetable fossil_." 272. _What is meant by a vegetable fossil?_ It is a substance _originally vegetable_, which, by pressure and other agencies within the earth, has been brought to a condition approaching that of _mineral_ or earthy matter. 273. _Why do we know that coal is of vegetable origin?_ By the _chemical components_ of its substance; and also by the _vegetable forms_ that are found abundantly in coal beds.