There is nothing in Nature more striking to the novice than the first suggestions of the various, and apparently contradictory, at least unexpected, positions in which the same mineral is found.  Now carbon is one of the minerals whose exchanges are peculiarly interesting.  Chemists say that the diamond is the only instance in Nature of pure carbon:  it burns in oxygen under the influence of intense heat, and leaves no ashes.  Next to this—­strange gradation!—­is charcoal, which comes within a very little of being a diamond.  But just that little interval is apparently so great, that none but a chemist would suspect there was any relationship between them.  Then come all those immense beds of coal which compose one of the geological strata of the earth’s crust, a stratum that was formed before the appearance of the animated creation, when the earth was clothed with a gigantic forest, whose mighty trunks buried themselves with their fallen leaves, and became, in time, a continuous bed of carbonaceous stone.

If we look at the vegetable and animal kingdoms, we find carbon entering into the composition of every tissue.  But there are certain tissues and anatomical elements (as physicians say) which are formed largely of carbon and have no nitrogen whatever.  These are oils and fats and everything related to them.  What will be chiefly interesting, however, to our readers, is the power of transformation of one of these substances into another.  Starch, gum, and sugar can all be changed into fat.  The explanation of it is in the fact, that these substances are all chemically alike,—­that is, they all have nearly the same proportions of carbon, oxygen, and hydrogen, and no nitrogen; but by slight differences in the combination of these elements, they exist in Nature as so many distinct substances.  Their approach to identity is further confirmed by the fact, that starch can be made into gum, and either of them into sugar, in the laboratory.  The transformation of starch and gum into sugar is also constantly going on in the ripening of fruits.  When country-dames make currant-jellies and currant-wine, they know very well, that, if they allow the berries to get dead-ripe, their jelly will not be so firm as when they seize an early opportunity and gather them when first fully red.  They may also have observed that jelly made late, besides being less firm, is much more likely to candy.  At first, the currants contain hardly any sugar, but more gum and vegetable jelly (glue); when dead-ripe, they have twelve times as much sugar as at first, and the gum and glue are much diminished.  The gummy and gluey materials have been transformed into sugar.  Every ripe fruit gives us evidence of the same manufacture of sugar that has gone on under the stimulus of the sun’s rays; and in the greatest source of sugar, the cane, the process is the same.  A French physician, M. Bernard, has, within the last twelve years, discovered that the liver of animals is constantly making sugar out of all kinds of food, while the lungs are all the time undoing the work of the liver and turning it back into its chemical elements.  And although, in the laboratory of the liver, it is discovered that no alimentary substance is quite deficient in sweetness, yet there, as elsewhere, starch and gum yield a far greater amount of it than animal substances.