such a case the desired result is obtained by the method of means or averages; this method equalises all irregular or accidental changes, and thus enables the regular ones to be perceived. It is very largely employed in meteorological investigations, to determine the average height of the mercury in a barometer, the average temperature of the earth, or velocity of the wind, the changes of magnetism, &c., at any period; also to find the true sea-level or height of tide, and so on. In this way, quantitative determinations often enable us to discover a cause, or an effect, and its amount at the same time.1 CHAPTER XLVII. DISCOVERY OF STATIC CONDITIONS. STATIC Conditions are essentially of greater importance than dynamic ones, and the minute circumstance which excites, liberates, determines, transmutes, directs, and guides a force, is often more influential (especially when aided by time) than the force itself. This great truth is manifested in every science and branch of knowledge. In the science of heat, unless the fire of a locomotive be excited by applying a match, no steam will be generated ; in that of mechanical power, unless the valve of the engine is open, to liberate steam from the boiler into the cylinders, no motion occurs; and upon a railway, unless the points of the rails are properly placed, an accident soon occurs ; in that of electricity, unless a telegraphic circuit throughout is complete, no message can be sent. In the sciences of physiology and psychology also the same truth appears ; 1 See also page 423. men must be active whether they are willing or not, and the great problem of life is not so much how to exercise the greatest physical activity or mental enthusiasm, as how to properly excite, transmute and direct that activity. The most Godlike ability is not mere activity, but a rational use of it; and a properly directed body and mind is far more important than physical power, or unregulated mental action. Unregulated human power is often dangerous, and abundance of examples of the evil effects of it may be seen in the records of crime, in sectarian and political strife, and in lunatic asylums. A steam-boiler without a valve, a steam-engine without a governor or fly-wheel to regulate the speed, is a most dangerous instrument, and equally so are the actions of men when not regulated by knowledge and the powers of comparison and inference. The great effect of minute static conditions is manifest in a large variety and number of phenomena in every science without exception. For instance, the very smallest proportion of foreign substances dissolved in water greatly affects the phenomena of osmose, 'pedesis,' and electric conduction resistance of that liquid; the electric conductibility of copper is greatly diminished by a minute trace of arsenic in that metal; and that of alcohol is conspicuously affected by the most minute traces of various dissolved substances. A minute proportion of tin also considerably diminishes the ductility of gold. Conditions are of various kinds, and may be conveniently divided into real and apparent, immediate and remote, essential and non-essential, accidental, absorbing, exciting, releasing, transmuting, deflecting, guiding, limiting, accelerating, neutral, obstructive, preventive, &c. Those which are non-essential, accidental or neutral, I class under the separate head of coincidences for the sake of convenience of treatment, and because they are merely accompaniments KINDS OF STATIC CONDITIONS. 437 and take no real part in producing the effect. Conditions, like causes, may also be classed in a more scientific manner, according to the various sciences to which they belong, and which will probably be their classification when knowledge has sufficiently advanced; thus we may have conditions of time and space, mathematical and geometrical conditions of the masses, molecules, and atoms, static and dynamic mechanical conditions of the same, thermic, optic, electric, magnetic, chemical, vital, psychical conditions, &c., of them; and all the subdivisions of these. A real condition is one which is indispensable to the production of the effect in the particular instance; it is often more fundamental and comprehensive than the corresponding apparent one, because it agrees with the exceptional cases, whilst the apparent one does not. An apparent condition is one which appears to agree with all the phenomena, but which, on deeper or more extensive. examination, fails generally or in certain cases; thus Ampère's theory that magnetism is due to innumerable electric currents continually flowing in one uniform direction round the molecules of the iron, agrees admirably with all the phenomena of electro-magnetic attraction, repulsion, and motion, but is defective, because there is no known instance of electric currents being maintained without a continual consumption of power and evolution of heat; but in magnets there is no such source of power, and no evolution of heat. An essential condition is one without which the effect cannot be produced even in the smallest degree. A releasing or exciting condition is one which enables a latent force to become free, and excites it to operate ; it takes only an apparent and not any real part in producing the effect due to the liberated force. Its action is essentially distinct: for instance, friction excites and : 6 releases the pent-up power in a match; taps and cocks, pendulums of clocks, also, are releasing conditions of mechanical power; a certain temperature is a releasing condition of latent heat in the freezing of water, but the lowering of temperature of the water, and the sudden evolution of latent heat, are two essentially different things; similarly, raising the temperature of explosive antimony' to its discharging point, and the sudden evolution of heat, are each distinct phenomena. Even at ordinary temperatures some substances unite chemically, and evolve heat when brought into mutual contact; phosphorus and iodine, for example; also arsenic and chlorine; and in each of these cases a certain range of temperature acts as a releasing and exciting condition. Now it cannot be that free heat is required in either case, because heat is evolved by the action, and what the temperature does is quite a different thing from supplying heat. The human will is probably a realising condition. Whether a force shall be liberated and become active or not, depends both upon the presence of some releasing condition and upon the absence of all those which are preventive. Some releasing conditions are self-acting, such as ball-cocks, overflow dams and syphons, and other contrivances. Transmuting conditions are highly important, especially those which cause one form of energy to be changed into another. It would be a great advance made in science to discover the geometric and mechanical conditions of the molecules which determine the change of refrangibility of light and of heat, of the change of heat into electricity, of electricity into chemical power, &c. &c. In each of such cases there must exist a condition (or conditions) which determines the change, and that condition must be of a fundamental character. In the absence of transmuting conditions and of preventive ones, similar causes must produce similar effects; but we know that in a great variety and number of cases similar causes produce dissimilar or even opposite effects, and therefore the sphere of influence of transmuting conditions is a very great one. A determining, deflecting, or guiding condition is one which decides the kind or direction of effect which an active force produces: for instance, railway points determine the direction in which a train shall proceed, telegraphic switches determine that in which a message shall be sent; reflectors, lenses, and prisms direct the course of rays of light; conducting wires determine the course of an electric current, &c. &c. Carbon and oxygen unite together chemically at a red heat, because the determining or guiding condition (consisting probably of suitable relative molecular states of the two substances) is present; but carbon and chlorine will not chemically unite at any temperature, because such a determining condition is not present. When a force is active, it always produces some effect, and the effect it produces is usually more or less different in different cases: thus, heat applied to ice, melts it; to water, converts it into a vapour; to steam, enlarges its bulk; to a thermo-electric pile, produces an electric current; to a magnet, destroys its magnetism; to oxide of silver, decomposes it; to a mixture of oxygen and hydrogen, causes them to combine, and produce an explosion; and so on. And, under different determining conditions, even opposite effects are sometimes due to the same cause: for instance, a ball of iron sink in water, but rises in mercury by the attractive force of gravity. Not only does the same cause produce different and even opposite effects under the guidance of different conditions, but different causes sometimes produce the same effect: for instance, an electric current may be produced by means of friction in an ordinary |