Page:Harper's New Monthly Magazine - v108.djvu/747

Rh ly developed plant is compelled to pursue is, of course, denied inorganic bodies. If, however, we observe the procreative process in the lowest orders of plant life, as characterized by a simple division or expulsion of cells, we shall experience no difficulty in recognizing a transition to the world of inorganic matter. Each particle of a piece of alum broken off has an independent power of growth when surrounded by conditions conducive to such growth—i. e., by suspending it in a solution saturated with alum; that is to say, if, under favorable conditions, we enable water and the original components of alum to come into contact with the crystal germ.

The similarity in the composition of our metals (belonging to the inorganic world) and the composition and growth of vegetable and animal parts is surprising. Fig. 1 represents a 300-fold magnified section of annealed soft-steel wire. Does the picture not remind us of the tiny microscopic cells which make up the texture of plants? The similarity is so striking that the well-known scientist Osmond has in part made use of the same as a basis for his cellular theories of iron and steel. The single particles of which metal is composed are generally styled "crystals" and not "cells." Similar in its structure to iron, copper consists of thousands of little crystals, as shown by the microphotograph in Fig. 2, representing the structure of a copper wire magnified 360 times.

This cellular, or, more properly speaking, crystalline, structure of metals is by no means rigid and unchangeable; on the contrary, it is astonishing how much life is, under certain circumstances, displayed in a piece of copper or iron. Of course such life processes do not work so imposingly as analogous processes in the vegetable kingdom. In the case of metals we are obliged to call in the aid of the microscope in order to observe such life processes, whereupon a surprising and multifarious change is afforded the eye. Also, the conditions under which such processes are going on are in certain respects analogous to those displayed by plant life. When the poet paints to us in glowing colors the joyous return of spring, after winter's dark night and the awakening of nature, the latter donning her most attractive garb, such enthusiastic delineation is, in a prosaic rendering, nothing more nor less than saying that the warm rays of the sun in the spring increase the temperature of the earth and atmosphere. Such rise in temperature is one of the necessary conditions for the life process of plants, which may repeat itself periodically or come to an end in one cycle. Thanks to the warmth afforded by the sun's rays, from the matter supplied from the soil and atmosphere the plant is enabled to build up cell after cell. In the case of metals much greater changes of temperature are necessary than for releasing life processes in plants. Whereas the life of the plant is limited to comparatively slight changes in atmospheric temperature, metals and inorganic bodies in general retain their vitality within far greater limits of temperature.

For instance, by heating a piece of copper an impulse is given tending to release the active internal powers of this seemingly lifeless metal. The eye of the investigator observes how its single cells or crystals begin to grow, though the piece of copper externally does not undergo any change as to form or size. The cells or crystals, originally small, combine to form larger crystals, this process continuing until a maximum value of size of the crystals, corresponding to a certain temperature, is attained. Whereas at the beginning of the heating process growth proceeds very rapidly, it gradually becomes slower and slower according as the size of the crystals approaches the maximum value named, finally coming to a standstill. Any further increase of temperature is accompanied by a further growth of the crystals, until a new limit, corresponding to the new temperature, is gradually reached. Fig. 3 illustrates this process. The left half of the illustration, magnified twenty-nine times, represents the structure of a copper wire after having been exposed half an hour to 1015° C. of heat. The right half of the figure shows us the same wire after being exposed two and a half hours to the same degree of heat—1015° C. The growth of the crystals thus resulting is apparent. If we imagine these crystals, in general