The immense preponderance of the vegetable over the animal world in quantity compensates somewhat for the superior organisation and the intelligence of the latter, which must be studied in the individual, while the vegetable world, which can be contemplated in the mass, almost overwhelms the imagination with its vastness. It is indeed impossible to compute the amount of vegetation in the great forests of America and Russia (in which latter country are the largest in the world), covering hundreds, nay thousands, of square miles with one continuous growth of timber. That forest in Russia through which the river Pechora flows, extends over a space of 150,000 square miles! The whole mass of animated existence sinks into insignificance when compared in quantity with this; and when to these forest-tracts are added the thousands of square miles of grass and heaths which grow in some climates with wonderful luxuriance, the amount of the vegetable kingdom is at once placed beyond all comparison with the animal kingdom in point of quantity. Cooper, in his American novels, describes the prairies as great seas of grass extending as far as the eye can reach, and rising to a height of 8 or 10 feet; and Humboldt describes some of the grasses on the plains of the Oronoco, as being so gigantic that they measure 18 feet from knot to knot, and says the Indians use them for blow-pipes to shoot their poisoned arrows from. And--as though it were not sufficient that the earth should bring forth everywhere all kinds of trees, shrubs, and grasses--the waters of the ocean itself are often filled with vegetable life; in some tracks the tangled sea-weed (_Fucus Natans_) is so dense as to impede the onward progress of ships for hundreds of miles together. Humboldt, in his "Views of Nature," describing the two great banks of sea-weed, says: "The two banks of sea-weed, together with the transverse band uniting them, constitute the Sargasso Sea of the older writers, and collectively occupy an area equal to six or seven times that of Germany." [Illustration: FIG. 1.--DIATOMA VULGARIS.] [Illustration: FIG. 2.--VARIOUS DIATOMACEÆ.]