Snowflakes copied from nature under the microscope, and serving to illustrate the geometrical arrangement of molecules of water in crystallizing. _a_, _b_, simple stars; _c_, _d_, hexagonal plates; _e_, _f_, rays of large and complex star-shaped flakes. The law of arrangement of the molecules is that of attraction in the lines of three axes at angles of sixty degrees, and the varieties are produced by differences in temperature and rate of supply of material.]
A lump of coal at first suggests little to excite interest or imagination; but the student of its composition and microscopic structure finds that it is an accumulation of vegetable matter representing the action of the solar light on the leaves of trees of the Palæozoic Age. It thus calls up images of these perished forests and of the causes concerned in their production and growth, and in the accumulation and preservation of their buried remains. It further suggests the many ways in which this solar energy, so long sealed up, can be recalled to activity in heat, gaslight, steam, and electric light, and how remarkably these things have been related to the wealth and the civilization of modern nations. An able writer of the agnostic school, in a popular lecture on coal, has his imagination so stimulated by these thoughts that he apostrophizes "Nature" as the cunning contriver who stored up this buried sunlight by her strange and mysterious alchemy, kept it quietly to herself through all the long geological periods when reptiles and brute mammals were lords of creation, and through those centuries of barbarism when savage men roamed over the productive coal-districts in ignorance of their treasures, and then revealed her long-hidden stores of wealth and comfort to the admiring study of science and civilization, and for the benefit of the millions belonging to densely-peopled and progressive nations; It is plain that "Nature" in such a connection represents either a poetical fiction, a superstitious fancy, or an intelligent Creative Mind. It is further evident that such Creative Mind must be in harmony with that of man, though vastly greater in its scope and grasp in time and space.
Even the numerical relations observed in nature teach the same lesson. The leaves of plants are not arranged at random, but in a series of curiously-related spirals, differing in different plants, but always the same in the same species and regulated by definite laws. Similar definiteness regulates the ramification of plants, which depends primarily on the arrangement of the leaves. The angle of ramification of the veins of the leaf is settled for each species of plant; so are the numbers of parts in the flower and the angular arrangement of these parts. It is the same in the animal kingdom, such numbers as 5, 6, 8, 10 being selected to determine the parts in particular animals and portions of animals. Once settled, these numbers are wonderfully permanent in geological time. The first known land reptiles appear in the Carboniferous period, and they have normally five toes; these appear in the earliest known species in the lowest beds of the Carboniferous. Their predecessors, the fishes, had numerous fin-rays; but when limbs for locomotion on land were contrived, the number five was adopted as the typical one. It still persists in the five toes and fingers of man himself. From these, as is well known, our decimal notation is derived. It did not originate in any special fitness of the number ten, but in the fact that men began to reckon by counting their ten fingers. Thus the decimal system of arithmetic, with all that follows from it, was settled millions of years ago, in the Carboniferous period, either by certain low-browed and unintelligent batrachians or by their Maker.