We cannot therefore deal with Earth as we have dealt with its mighty brethren; we cannot deduce any general conclusions as to its nature from the analysis of a single sample. We may resolve a particular handful of soil into its elements, but we dare not assert that these elements are common to the multitudinous handfuls which constitute the solid portions of our planet.
How, then, are we to proceed with our investigations? Were we to examine in regular order the various compounds included in the ancient conception of earth, our fairy tale would assume the character and proportions of an encyclopaedia. To preclude such a result, we must abandon the analytical method of inquiry, and be content to accept certain comprehensive truths that chemistry has revealed regarding the constitution of different kinds of earth.
The diversified compounds which form the material world have been resolved by the chemist into sixty-three elementary bodies, fifty of which are metals. These elements are rarely found in a state of purity, owing to their strong tendency to combine with each other.
The principal ingredients of Earth, are compounds of oxygen with certain elementary bodies that are never found pure in nature.
Silica, the most widely-diffused compound, contains oxygen, and another of the metalloids, or nonmetallic elements, called silicon, which can be
