Popular Science Monthly/Volume 11/June 1877/Initiatory Forces

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LAST September, when the operations for the removal of the obstructions at Hell-Gate, in the harbor of New York, had culminated in the completion of the great labyrinth of tunnels, and the storing therein of a larger quantity of explosives than had ever been used at once before. General Newton, the chief-engineer, at the appointed moment told his little child to gently push a telegraph-key. She did so; her tiny impulse closed the circuit in many hundred galvanic cells; and these, by inflaming the metallic wires in contact with the explosives, freed in an instant the tremendous power which had been slumbering under the peaceful waters.

Perhaps in the whole realm of human achievement no more striking-example of an initiatory force has ever been given than this. And if it had not had an appearance of trifling, it would doubtless have been quite possible for matters to have been so arranged that a fly imprisoned in an inverted wineglass could by the vibration of its little wings have brought two delicate electric conductors into contact—say two moistened silken filaments—and have thus pulled the trigger which, in the course of its effects, would have made Hell-Gate navigable.

In Nature and art we find abundant examples of the same kind: gigantic forces, perfectly quiescent and even useless, until some slight additional force of the proper kind or intensity precipitates the most violent changes. And this necessity for an outside initiatory force is generally found with great power to maintain action once begun. Carbon, and fuels of all kinds, are instances in point. As a rule, they are but little altered by contact with the atmosphere, even for years; but a match has only to be applied to a few shavings, and a mine of coal may be set on fire so thoroughly that it continues burning for half a century. A prairie or forest may be dried up by drought until leaves and twigs are brittle and dead, but all is calm until a chance spark from a locomotive or a tobacco-pipe starts a fire that may devastate square leagues of territory in its course.

In all cases of unstable equilibrium—and such abound in Nature—a very small impetus may produce great consequences; and this not only in amount but direction. With an avalanche perched on a mountain-peak, it has often been a very slight force that has determined the path it has taken, and which of two villages miles apart was to be demolished by it. The fire-alarm system in our cities uses electricity as an initiatory motion: the hammers of the tower-bells are worked by the descent of heavy weights—wound up by manual power from time to time—and the store of energy contained in the elevated masses is instantly made available by an electric current from the central office simply freeing a detent and allowing the weight to fall. Many other recent inventions for working railway-signals, looms, etc., embody this principle. The magneto-electric machines, which are extensively employed in lighthouses and electro-plating factories, yield electricity from the mechanical motion of a steam-engine. A small permanent steel magnet is indispensable in the apparatus; it induces magnetism in soft-iron cores, and these again in others in an increasing series. The power may be gigantic, and the magnet, were it not inconvenient, might be as small as a cambric needle: yet without it neither electricity nor light can be had. A similar illustration occurs in the development of a current in a common galvanic battery: the two pieces of different metals used, as zinc and copper, when quite dry before being placed in the bath, if simply brought into contact for a moment show opposite electric polarities which, if given a mechanical expression, would be a very small amount indeed. This minute force, only to be detected by the most delicate means, is the necessary opening of the flood-gate of energy in a working battery. And when light is desired from a group of powerful cells, it is first requisite to use a small effort in bringing the poles together, and then separating them at a short distance apart. The brilliant arc of light, once across the chasm, can continue to span it; but its force, although so great, is unequal to leaping over it without help. These examples show the importance of knowing the fit initiatory forces in processes whereby one form of energy is sought to be converted into another. It is probably for lack of such knowledge that at present we waste so lamentable a quantity of heat, our commonest force, in changing it into the more desirable form of electricity, light, and mechanical motion. In exceptionally favorable circumstances, steam-engines of the best kind give but a fourth in work of the theoretical value of the heat applied, and in obtaining an electric current from an engine further loss occurs; while the production in a thermo-battery of a current from heat directly has never yet yielded as much as one-hundredth of the force employed.

A slight and well-aimed effort may not only free an immense magazine of energy, but also give it a particular direction and pilot it into one or. another of two entirely new seas. Hydrogen and oxygen gases in separate receivers might remain tranquil and unchanged for ages, and it depends upon the choice of the experimenter, when he wishes to render their energy available, whether their intense chemical force shall take the form of heat or give forth an electric current. In the former case he shall connect the receivers together by suitable tubes, apply a spark, and obtain a flame hot enough to fuse and vaporize iron or platinum. In the other case he can use Grove's gas-battery, and permit the elements to unite into water, producing an intense electric current capable of working scores of miles of telegraph. The realm of light yields us examples analogous to those given in the domains of heat and electricity. In photography it has been discovered that blue rays may begin an impression which red or yellow ones can finish, and finish only. The power of continuance is different from the power of initiation, and depends upon it for its opportunity of usefulness.

The instability of equilibrium among forces brings in an element of uncertainty, or rather incalculability, which renders prediction extremely difficult in many fields of scientific investigation. Prof. Balfour Stewart, in a most instructive essay on "Solar Physics," gives us some illustrations of this. He supposes a stratum of air in the earth's atmosphere to be very nearly saturated with aqueous vapor; that is to say, just a little above the dew-point; while at the same time it is losing heat with extreme slowness, so that if left to itself it would be a long time before moisture were deposited. Now, such a stratum is in an extremely delicate state of molecular equilibrium, and the dropping into it of a small crystal of snow would at once cause a remarkable change of state. For what would happen? The snow would cool the air around it, and thus moisture would be deposited in the form of fine mist or dew. Now, this deposited mist or dew, being a liquid, and as such much more radiant than vapor, would send its heat into empty space much more rapidly than the saturated air; and therefore it would become colder than the air around it. Thus, more air would be cooled, and more mist or dew deposited; and so on until a complete change of condition should be brought about, resulting perhaps in a shower of rain. Now, in this imaginary case, the tiniest possible flake of snow has pulled the trigger, as it were, and made the gun go off—has changed completely the whole arrangement that might have gone on for some time longer as it was, had it not been for the advent of the snow-flake. Prof. Stewart thus points out that the presence of a condensable liquid in our atmosphere adds an element of violence, and also of abruptness, amounting to incalculability, to the motions which take place. Hence meteorology must long, if not ever, remain an incomplete science, since in its problems so many variable and unstable factors occur. In the course of the same essay Prof. Stewart tells us how parallelism has been observed between three very interesting classes of phenomena, namely, the periods of maximum sunspots, of brilliant auroral displays, and of great disturbances in the earth's magnetism. Extended observatory records show that all three coincide in their fluctuations; hence endeavors have been made to trace them to a common source. Observations at Kew for a series of years have detected that the proximity of Mercury and Venus to the sun seems to control the size and direction of the solar spots; and therefore it appears that these planets mediately through the sun cause our auroras and magnetic storms. There is also reason to believe that the production of sun-spots diminishes by absorption the actinic rays, while the thermal ones are not noticeably affected; for to the actinic rays the chemical or ripening effect is due. Years of minimum sun-spots have been found to coincide very nearly with the good wine years in Germany. At first sight we are startled by the supposition that a planet like Venus, which comes nearer to the earth than it ever does to the sun, should in any way be accountable for such enormous manifestations of energy as those which occur over the sun's surface. But the wonder will disappear if we bear in mind that there may be two kinds of causes or antecedents. Thus, we say that the blacksmith is the cause of the blow which his hammer strikes the anvil, and here the strength of the blow depends upon the strength of the smith. But we may likewise say that the man who pulls the trigger of a gun or cannon is the cause of the motion of the ball, and here there is no relation between the strength of the effect and that of its cause. Now, in whatever mysterious way Venus and Mercury affect the sun, we may be sure it is not after the fashion of the blacksmith: they do not deal him a violent blow producing all this enormous effect, but they rather pull the trigger, and immediately a very great change takes place. And, in passing, we are here taught how involved the relations of the parts of the universe may be. Two planets whose direct influence on the earth by their gravitation and light is quite inconsiderable, yet, by their indirect effects through their action on the sun, produce very marked and varied results on the surface of our globe. Many laboratory experiments, on a small scale, illustrate the potency of initiatory forces. A pail of water, maintained in great stillness, may be gradually chilled several degrees below the common freezing-point, when the formation of a cake of ice instantly follows from a slight shake. A clean glass vessel may be filled with water and slowly brought to a temperature in excess of the ordinary boiling-point, and a feeble shock is all that is needed for the prompt liberation of a large volume of steam. Crystallization offers similar results. A supersaturated solution of a salt may long remain in the liquid state until a crystalline fragment thrown in instantly serves as a nucleus for extensive solidification. When such a solution contains two salts, which begin to crystallize about the same temperature, when a solid fragment of each kind is thrown into the liquid, it picks out its kindred without the slightest error, and grows thereby. A new surgical method for covering a wound with skin employs as centres of growth tiny morsels of skin supplied from elsewhere. These gather together elements akin to themselves, and soon repair the injury, otherwise very slow at healing. In some similar way it must be that a small seed of a plant selects just such ingredients from the soil as shall make it thrive and increase. On these organic powers of initiation and selection, Lucretius ponders in his great poem, and wonders how it is that different animals—the pig, dog, and fowl—eat the same food and yet make of it such diverse substance. On a seed's peculiar nature it may follow whether a field shall give its substance to maples or cabbages. Just so a volcanic island's population depends, to a large extent, on the first comers—on what human tribe first lands there, what seeds and insects are first wafted upon it, and what birds first alight on its shores. Once in possession, the process of multiplication soon renders occupancy by stray creatures of superior kinds impossible; and so we have incidentally a case where the best may not be the conquerors and survivors. Mere precedence in time is often of much account. No man shall ever have as many children as Adam. The first poets exhausted the most striking and beautiful similes in Nature, such as now may independently but uselessly occur to every cultured imagination. The limits of choice in the subjects for invention, authorship, and art, are constantly narrowed by the occupation of territory by those who have gone before. Of course, infinite additions to knowledge and achievement are possible, but many efforts suggested by the wants of the time, though quite original, are fruitless simply because they do not happen to be first.

With respect to the great effectiveness of force, when used largely or totally in initiation, Prof. Stewart thinks that intelligence depends on conditions in the organism of unstable equilibrium, and he draws a parallel between the great powers of a human mind and the marked decomposibility of its brain-substance. The particular supremacy of man in Nature is thus traced to a principle which highly characterizes his own frame, and of which he avails himself in his mastery of external Nature—delicacy of poise in construction rendering large powers obedient to slight ones.

Our subject further suggests the importance of leadership among mankind. Heroes have been so unduly praised that a reaction has set in with many thinkers, who would detract from their real value. Popular discontent, or a wide-spread spirit of enterprise, often lingers in useless agitation for want of some man a little bolder than the rest, who shall make the first onslaught on tyranny, or captain the first ship that shall set its prow toward the shores of a new world. To be sure, a hero is no more than a representative of the strong feelings of his land and time; yet, without his faith and enthusiasm, perhaps but little more than that of many of his neighbors, their desires and hopes might never have fulfillment.

Finally, our theme shows us the immense difficulties in the way of reducing some inquiries of deep interest to exact treatment. If the problems of meteorology are of baffling intricacy, how much more so are those of history, with their elements of ignorance, of passion, and caprice—all controlling forces vastly greater than themselves! We have recently seen a few votes among hundreds decide the administration of the republic for years; and, within a decade, have beheld a single general's timidity or treachery betray a noble army into the enemy's hands, involving wide-spread ruin and deep national disgrace. And how often are our own individual lives utterly changed in purpose by a mere word, a smile, or a tear!