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And the same holds good for humanity. If it is thus with the individual, so it is likewise with humanity. For centuries nations may live under forms that meet their requirements, forms suitable to a feeble state; but it is altogether illusory to suppose that such an adaptedness can continue for ever. A critical eye discerns that the mental features of a given generation have become different from those of its ancestors. New ideas and a new manner of action are the tokens that a modification has silently taken place. Though after a short interval the change might not amount to much, in the course of time there must inevitably be exhibited the spectacle of a society that had outgrown its forms, its rules of life.

Wherever, then, such a want of harmony becomes perceptible, where the social system is incompatible with the social state, and is, in effect, an obsolete anachronism, it is plainly unphilosophical and unwise to resort to means of compulsion. No matter what the power of governments or of human authorities may be, it is impossible for them to stop the intellectual advancement, for it forces its way by an organic law over which they have no kind of control.

Summary of the investigation of the position of man. Astronomers sometimes affirm that the sun is the cause, directly or indirectly, of all the mechanical movements that take place upon the earth. Physiologists say that he is the generator of the countless living forms with which her surface is adorned.

Influence of the sun on inorganic nature, If the light, the warmth, and other physical influences of the sun could be excluded, there would be a stagnant and icy sea encircling silent and solitary shores. But the veil once withdrawn, or the influences permitted to take effect, this night and stillness would give place to activity and change. In the morning beams of the day, the tropical waters, expanding, would follow from east to west the course of the sun, each renewed dawn renewing the impulse, and adding force to the gentle but resistless current. At one place the flowing mass would move compactly; at another, caught by accidentally projecting rocks, it would give off little eddies, expending their share of its force; or, compressed in narrow passages, it would rush impetuously along. Upon its surface myriads of momentary ripples would play, or opposing winds, called into existence by similar disturbances in the air, would force it into waves, making the shores resound with their breaking surge. Twice every day, under the conjoint influences of the sun and moon, as if the inanimate globe itself were breathing, the tide would rise and fall again upon the bosom of the deep.

The eddy, the ripple, the wave, the current, are accidental forms through which the originally imparted force is displayed. They are all expending power. Their life, if such a term can be used, is not the property of themselves, but of the ocean to which they belong.

and on organic nature. Influences which thus metaphorically give life to the sea, in reality give life to the land. Under their genial operation a wave of verdure spreads over the earth, and countless myriads of animated things attend it, each like the eddies and ripples of the sea, expending its share of the imparted force. The life of these accidental forms, through which power is being transposed, belongs, not to itself, but to the universe of which it is a part.

Nature of animals. Of the waves upon the ocean there may not be two alike. The winds, the shores, their mutual interferences, a hundred extraneous influences, mould them into their ephemeral shapes. So those collections of matter of which animated things consist offer a plastic substance to be modified. The number of individuals counts like the ripples of the sea.

They constitute a series. As external circumstances change, animated forms change with them, and thus arises a series of which the members stand in a connected relation. The affiliated sequence of the external circumstances is represented in the affiliated succession of living types. From parts, or from things already existing, new parts and new things emerge, the new not being added or juxtaposed to the old, but evolved or developed from it. From the homogeneous or general, the heterogeneous or special is brought forth. A new member, fashioned in secrecy and apart, is never abruptly ingrafted on any living thing. New animal types have never been suddenly located among old ones, but have emerged from them by process of transmutation. As certainly as that every living thing must die, so must it reach perfection by passing through a succession of subordinate forms. An individual, or even a species, is only a zoological phase in a passage to something beyond. An instantaneous adult, like an immortal animal, is a physiological impossibility.

The doctrine of progressive improvement. This bringing forth of structure from structure, of function from function, incidentally presents, upon the whole, an appearance of progressive improvement, and for such it has been not unfrequently mistaken. Thus if the lowest animals, which move by reflex action instantly but unconsciously, when an impression is made upon them, be compared with the higher ones, whose motions are executed under the influence of antecedent impressions, and are therefore controlled by ideas, there seems to have been such an improvement. Still, however, it is altogether of a physical kind. Every impression of which the dog or elephant is conscious implies change in the nerve centres, and these changes are at the basis of the memory displayed by those animals. Our own experience furnishes many illustrations. When we gaze steadfastly on some brightly-illuminated object, and then close or turn aside our eyes, a fading impression of the object at which we have been looking still remains; or, when a spark is made to revolve rapidly, we think we see a circle of fire, the impression upon the retina lasting until the spark has completed its revolution. In like manner, though far more perfectly, are impressions registered or stored up in the sensory ganglia, the phantoms of realities that have once been seen. In those organs countless images may thus be superposed.

Analogies between animals and man. Man agrees with animals thus approaching him in anatomical construction in many important respects. He, too, represents a continuous succession of matter, a continuous expenditure of power. Impressions of external things are concealed in his sensory ganglia, to be presented for inspection in subsequent times, and to constitute motives of action. But he differs from them in this, that what was preparatory and rudimentary in them is complete and perfect in him. From the instrument of instinct there has been developed an instrument of intellection. In the most perfect quadrupeds, an external stimulus is required to start a train of thought, which then moves on in a determinate way, their actions indicating that, under the circumstances, they reason according to the same rules as man, drawing conclusions more or less correct from the facts offered to their notice. But, the instrument of intellection completed, it is quickly brought into use, and now results of the highest order appear. The succession of ideas is under control; new trains can be originated not only by external causes, but also by an interior, a spontaneous influence. The passive has become active. Animals remember, man alone recollects. Every thing demonstrates that the development and completion of this instrument of intellection has been followed by the super-addition of an agent or principle that can use it.

Points of distinction between them. There is, then, a difference between the brutes and man, not only as respects constitution, but also as respects destiny. Their active force merges into other mundane forces and disappears, but the special principle given to him endures. We willingly persuade ourselves that this principle is actually personified, and that the shades of the dead resemble their living forms. To Eastern Asia, where philosophy has been accustomed to the abstract idea of force, the pleasures we derive from this contemplation are denied, the cheerless doctrine of Buddhism likening the life of man to the burning of a lamp, and death to its extinction. Perceiving in the mutation of things, as seen in the narrow range of human vision, a suggestion of the variations and distribution of power throughout nature, it rises to a grand, and, it must be added, an awful conception of the universe.

But Europe, and also the Mohammedan nations of Asia, have not received with approbation that view. The human soul. To them there is an individualized impersonation of the soul, and an expectation of its life hereafter. The animal fabric is only an instrument for its use. The eye is the window through which that mysterious principle perceives: through the ear are brought to its attention articulate sounds and harmonies; by the other organs the sensible qualities of bodies are made known. From the silent chambers and winding labyrinths of the brain the veiled enchantress looks forth on the outer world, and holds the subservient body in an irresistible spell.

Extension of these views to the nature of the world. This difference between the Oriental and European ideas respecting the nature of man reappears in their ideas respecting the nature of the world. The one sees in it only a gigantic engine, in which stars and orbs are diffusing power and running through predestined mutations. The other, with better philosophy and a higher science, asserts a personal God, who considers and orders events in a vast panorama before him.

CHAPTER XI
THE EUROPEAN AGE OF REASON – (Continued)
THE UNION OF SCIENCE AND INDUSTRY

European Progress in the Acquisition of exact Knowledge. – Its Resemblance to that of Greece.

Discoveries respecting the Air. – Its mechanical and chemical Properties. – Its Relation to Animals and Plants. – The Winds. – Meteorology. – Sounds. – Acoustic Phenomena.

Discoveries respecting the Ocean. – Physical and chemical Phenomena. – Tides and Currents. – Clouds. – Decomposition of Water.

Discoveries respecting other material Substances. – Progress of Chemistry.

Discoveries respecting Electricity. Magnetism, Light, Heat.

Mechanical Philosophy and Inventions. – Physical Instruments. – The Result illustrated by the Cotton Manufacture. – Steam-engine. – Bleaching. – Canals. – Railways. – Improvements in the Construction of Machinery. – Social Changes produced. – Its Effect on intellectual Activity.

The scientific Contributions of various Nations, and especially of Italy.

The Age of Reason in Europe presents all the peculiarities of the Age of Reason in Greece. There are modern representatives of King Ptolemy Philadelphus among his furnaces and crucibles; of Hipparchus cataloguing the stars; of Aristyllus and Timochares, with their stone quadrants and armils, ascertaining the planetary motions; of Eratosthenes measuring the size of the earth; of Herophilus dissecting the human body; of Archimedes settling the laws of mechanics and hydrostatics; of Manetho collating the annals of the old dynasties of Egypt; of Euclid and Apollonius improving mathematics. Analogies between the Age of Reason in Europe and in Greece. There are botanical gardens and zoological menageries like those of Alexandria, and expeditions to the sources of the Nile. The direction of thought is the same; but the progress is on a greater scale, and illustrated by more imposing results. The exploring voyages to Madagascar are replaced by circumnavigations of the world; the revolving steam-engine of Hero by the double-acting engine of Watt; the great galley of Ptolemy, with its many banks of rowers, by the ocean steam-ship; the solitary watch-fire on the Pharos by a thousand light-houses, with their fixed and revolving lights; the courier on his Arab horse by the locomotive and electric telegraph; the scriptorium in the Serapion, with its shelves of papyrus, by countless printing-presses; the "Almagest" of Ptolemy by the "Principia" of Newton; and the Museum itself by English, French, Italian, German, Dutch, and Russian philosophical societies, universities, colleges, and other institutions of learning.

European progress in the acquisition of knowledge. So grand is the scale on which this cultivation of science has been resumed, so many are those engaged in it, so rapid is the advance, and so great are the material advantages, that there is no difficulty in appreciating the age of which it is the characteristic. The most superficial outline enables us to recognize at once its resemblance to that period of Greek life to which I have referred. To bring its features into relief, I shall devote a few pages to a cursory review of the progress of some of the departments of science, selecting for the purpose topics of general interest.

First, then, as respects the atmosphere, and the phenomena connected with it.

The atmosphere. From observations on the twilight, the elasticity of aerial bodies, and the condensing action of cold, the conclusion previously arrived at by Alhazen was established, that the atmosphere does not extend unlimitedly into space. Its height is considered to be about forty-five miles. From its compressibility, the greater part of it is within a much smaller limit; were it of uniform density, it would not extend more than 29,000 feet. Hence, comparing it with the dimensions of the earth, it is an insignificant aerial shell, in thickness not the eightieth part of the distance to the earth's centre, and its immensity altogether an illusion. It bears about the same proportion to the earth, that the down upon a peach bears to the peach itself.

A foundation for the mechanical theory of the atmosphere was laid as soon as just ideas respecting liquid pressures, as formerly taught by Archimedes, were restored, the conditions of vertical and oblique pressures investigated, the demonstration of equality of pressures in all directions given, and the proof furnished that the force of a liquid on the bottom of a vessel may be very much greater than its weight.

Its mechanical relations. Such of these conclusions as were applicable were soon transferred to the case of aerial bodies. The weight of the atmosphere was demonstrated, its pressure illustrated and measured; then came the dispute about the action of pumps, and the overthrow of the Aristotelian doctrine of the horror of a vacuum. Coincidently occurred the invention of the barometer, and the proof of its true theory, both on a steeple in Paris and on a mountain in Auvergne. The invention of the air-pump, and its beautiful illustrations of the properties of the atmosphere, extended in a singular manner the taste for natural philosophy.

Its chemical relations. The mechanics of the air was soon followed by its chemistry. From remote ages it had been numbered among the elements, though considered liable to vitiation or foulness. The great discovery of oxygen gas placed its chemical relations in their proper position. One after another, other gases, both simple and compound, were discovered. Then it was recognized that the atmosphere is the common receptacle for all gases and vapours, and the problem whether, in the course of ages, it has ever undergone change in its constitution arose for solution.

The antagonism of animals and plants. The negative determination of that problem, so far as a few thousand years are concerned, was necessarily followed by a recognition of the antagonism of animals and plants, and their mutually balancing each other, the latter accomplishing their duty under the influence of the sun, though he is a hundred millions of miles distant. From this it appeared that it is not by incessant interventions that the sum total of animal life is adjusted to that of vegetable, but that, in this respect, the system of government of the world is by the operation of natural causes and law, a conclusion the more imposing since it contemplates all living things, and includes even man himself. The detail of these investigations proved that the organic substance of plants is condensed from the inorganic air to which that of all animals returns, the particles running in ever-repeating cycles, now in the air, now in plants, now in animals, now in the air again, the impulse of movement being in the sun, from whom has come the force incorporated in plant tissues, and eventually disengaged in our fires, shining in our flames, oppressing us in fevers, and surprising us in blushes.

The winds; their origin and nature. Organic disturbances by respiration and the growth of plants being in the lowest stratum of the air, its uniformity of composition would be impossible were it not for the agency of the winds and the diffusion of gases, which it was found would take place under any pressure. The winds were at length properly referred to the influence of the sun, whose heat warms the air, causing it to ascend, while other portions flow in below. The explanation of land and sea breezes was given, and in the trade-wind was found a proof of the rotation of the earth. At a later period followed the explanation of monsoons in the alternate heating and cooling of Asia and Africa on opposite sides of the line, and of tornadoes, which are disks of air rotating round a translated axis with a diameter of one hundred or one hundred and fifty miles, the axis moving in a curvilinear track with a progressive advance of twenty or twenty-five miles an hour, and the motions being in opposite directions in opposite hemispheres of the globe.

The equatorial calms and trade-winds accounted for on physical principles, it was admitted that the winds of high latitudes, proverbially uncertain as they are, depend in like manner on physical causes.

With these palpable movements there are others of a less obvious kind. Through the air, and by reason of motions in it, sounds are transmitted to us.

Of sounds; their velocity. The Alexandrian mathematicians made sound a favourite study. Modern acoustics arose from the recognition that there is nothing issuing from the sounding body, but that its parts are vibrating and affecting the medium between it and the ear. Not only by the air-pump, but also by observations in the rare atmosphere of the upper regions, it was shown that the intensity of sound depends upon the density. On the top of a mountain the report of a pistol is no louder than that of a cracker in the valley. As to the gradual propagation of sounds, it was impossible to observe fire-arms discharged at a distance without noticing that the flash appears longer before the report in proportion as the distance is greater. The Florentine academicians attempted a determination of the velocity, and found it to be 1148 feet in a second. More accurate and recent experiments made it 1089·42 feet at the freezing-point of water; but the velocity, though independent of the density, increases with the temperature at the rate of 1·14 foot for each degree. For other media the rate is different; for water, about 4687 feet in a second, and in cast iron about 10 ½ times greater than in air. All sounds, irrespective of their note or intensity, move at the same velocity, the medium itself being motionless in the mass. No sound can pass through a vacuum. The sudden aerial condensation attending the propagation of a sound gives rise to a momentary evolution of heat, which increases the elasticity of the air, and hence the velocity is higher than 916 feet in a second, otherwise the theoretical rate.

Acoustic phenomena. Turning from soniferous media to sounding bodies, it was shown that the difference between acute and grave sounds depends on the frequency of vibration. The ear can not perceive a sound originating in less than thirty-two vibrations in a second, nor one of more than 24,000. The actual number of vibrations in a given note was counted by means of revolving wheels and other contrivances. I have not space to relate the investigation of many other acoustic facts, the reference of sounds to phases of condensation, and rarefaction in the elastic medium taking place in a normal direction; the affections of note, intensity, quality; the passage in curved lines and around obstacles; the production of sympathetic sounds; nodal points; the effect of reeds; the phenomena of pipes and flutes, and other wind instruments; the various vibrations of solids, as bells; or of membranes, as drums; visible acoustic lines; the reflexion of undulations by surfaces of various forms; their interferences, so that, no matter how intense they may be individually, they can be caused to produce silence; nor of whispering galleries, echoes, the nature of articulate sounds, the physiology of the vocal and auditory organs of man, and the construction of speaking machines.

The ocean; its size. Like the air, the ocean, which covers three-fourths of the earth's surface, when reduced to a proper standard of measure, loses very much of its imposing aspect. The varnish that covers a twelve-inch globe represents its relative dimension not inadequately.

Tides and currents. On the theory of gravitation, the tides of the ocean were explained as depending on the attractive force of the sun and moon. Its currents, in a general manner, are analogous to those of the air. They originate in the disturbing action of solar heat, the temperature of the sea varying from 85° in the torrid zone to the freezing-point as the poles are approached. Its specific gravity at the equator is estimated at 1·028; but this density necessarily varies with the rate at which superficial evaporation takes place; the pure vapour rising, leaves a more concentrated salt solution. The effect is therefore, in some degree, to counteract the expansion of the water by warmth, for the sun-rays, being able to penetrate several feet below the surface, correspondingly raise the temperature of that portion, which expands and becomes lighter; but, simultaneously, surface evaporation tends to make the water heavier. Notwithstanding this, currents are established through the preponderance of the dilatation, and of them the Gulf Stream is to us the most striking example.

Effects of ocean streams. The physical action of the sun-rays in occasioning currents operates through the expansion of water, of which warm portions ascend to the surface, colder portions from beneath setting in to supply their place. These currents, both hot and cold, are affected by the diurnal rotation of the earth, the action being essentially the same as that for the winds. They exert so great an influence as conveyers of heat that they disturb the ordinary climate relation depending on the sun's position. In this way the Gulf Stream, a river of hot water in a sea of cold, as soon as it spreads out on the surface of the Atlantic in higher latitudes, liberates into the air the heat it has brought from the torrid zone; and this, being borne by the southwest wind, which blows in those localities for the greater part of the year, to the westerly part of the European continent, raises by many degrees the mean annual temperature, thus not only regulating the distribution of animals and plants, but also influencing human life and its pursuits, making places pleasant that would otherwise be inclement, and even facilitating the progress of civilization. Whatever, therefore, can affect the heat, the volume, the velocity, the direction of such a stream, at once produces important consequences in the organic world.

Physical and chemical relations of water. The Alexandrian school had attained correct ideas respecting the mechanical properties of water as the type of liquids. This knowledge was, however, altogether lost in Europe for many ages, and not regained until the time of Stevinus and Galileo, who recovered correct views of the nature of pressure, both vertical and oblique, and placed the sciences of hydrostatics and hydrodynamics on exact foundations. The Florentine academicians, from their experiments on water inclosed in a globe of gold, concluded that it is incompressible, an error subsequently corrected, and its compressibility measured. The different states in which it occurs, as ice, water, steam, were shown to depend altogether on the amount of latent heat it contains. Out of these investigations originated the invention of the steam-engine, of which it may be said that it has revolutionized the industry of the world. Soon after the explanation of the cause of its three states followed the great discovery that the opinion of past ages respecting its elementary nature is altogether erroneous. It is not a simple element, but is composed of two ingredients, oxygen and hydrogen, as was rigorously proved by decomposing and forming it. By degrees, more correct views of the nature of evaporation were introduced; gases and vapours were found to coexist in the same space, not because of their mutual solvent power, but because of their individual and independent elasticity. The instantaneous formation of vapours in a vacuum showed that the determining condition is heat, the weight of vapour capable of existing in a given space being proportional to the temperature. More scientific views of the nature of maximum density were obtained, and on these principles was effected the essential improvement of the low pressure steam-engine – the apparent paradox of condensing the steam without cooling the cylinder.

In like manner much light was cast on the meteorological functions of water. It was seen that the diurnal vaporization from the earth depends on the amount of heat received, the vapour rising invisibly in the air till it reaches a region where the temperature is sufficiently low. There condensation into vesicles of perhaps 1/50000 of an inch in diameter ensues, and of myriads of such globules a cloud is composed. Clouds and their nomenclature. Of clouds, notwithstanding their many forms and aspects, a classification was given – cirrus, cumulus, stratus, etc. It was obvious why some dissolve away and disappear when they encounter warmer or drier spaces, and why others descend as rain. It was shown that the drops can not be pure, since they come in contact with dust, soluble gases, and organic matter in the air. The return of water to the sea. Sinking into the ground, the water issues forth as springs, contaminated with whatever is in the soil, and finds its way, through streamlets and rivers, back to the sea, and thus the drainage of countries is accomplished. Through such a returning path it comes to the receptacle from which it set out; the heat of the sun raised it from the ocean, the attraction of the earth returns it thereto; and, since the heat-supply is invariable from year to year, the quantity set in motion must be the same. Collateral results of no little importance attend these movements. Every drop of rain falling on the earth disintegrates and disturbs portions of the soil; every stream carries solid matter into the sea. It is the province of geology to estimate the enormous aggregate of detritus, continents washed away and new continents formed, and the face of the earth remodelled and renewed.

Progress of chemistry. The artificial decomposition of water constitutes an epoch in chemistry. The European form of this science, in contradistinction to the Arabian, arose from the doctrine of acids and alkalies, and their neutralization. This was about A.D. 1614. It was perceived that the union of bodies is connected with the possession of opposite qualities, and hence was introduced the idea of an attraction of affinity. On this the discovery of elective attraction followed. Then came the recognition that this attraction is connected with opposite electrical states, chemistry and electricity approaching each other. A train of splendid discoveries followed; metals were obtained light enough to float on water, and even apparently to accomplish the proverbial impossibility of setting it on fire. In the end it was shown that the chemical force of electricity is directly proportional to its absolute quantity. Attraction. The elements. Better views of the nature of chemical attraction were attained, better views of the intrinsic nature of bodies. The old idea of four elements was discarded, as also the Saracenic doctrine of salt, sulphur, and mercury. The elements were multiplied until at length they numbered more than sixty. Theory of phlogiston. Alchemy merged into chemistry through the theory of phlogiston, which accounted for the change that metals undergo when exposed to the fire on the principle that something was driven off from them – a something that might be restored again by the action of combustible bodies. It is remarkable how adaptive this theory was. It was found to include the cases of combustive operations, the production of acids, the breathing of animals. It maintained its ground even long after the discovery of oxygen gas, of which one of the first names was dephlogisticated air.

But a false theory always contains within itself the germ of its own destruction. The weak point of this was, that when a metal is burnt the product ought to be lighter than the metal, whereas it proves heavier. Introduction of the balance into chemistry. At length it was detected that what the metal had gained the surrounding air had lost. This discovery implied that the balance had been resorted to for the determination of weights and for the decision of physical questions. The reintroduction of that instrument – for, as we have seen, it had ages before been employed by the Saracen philosophers, who used several different forms of it – marked the epoch when chemistry ceased to be exclusively a science of quality and became one of quantity.

Theory of oxygen, and the nomenclature. On the ruins of the phlogistic theory arose the theory of oxygen, which was sustained with singular ability. Its progress was greatly facilitated by the promulgation of a new nomenclature in conformity to its principles, and of remarkable elegance and power. In the course of time it became necessary, however, to modify the theory, especially by deposing oxygen from the attitude of sovereignty to which it had been elevated, and assigning to it several colleagues, such as chlorine, iodine, etc. The introduction of the balance was also followed by important consequences in theoretical chemistry, among which pre-eminently was the establishment of the laws of combinations of bodies.