We spend our lives on the bottom of a vast ocean of air which is sodeep that no one has ever been able to reach the surface. During certain hours of every, day the whole of this vast air-sea is exposed to the rays of the sun.When that happens we say that it is light and that we can see.For we happen to belong to a species of living beings which is provided with a sense of vision and in the front of our head we carry two curiously shaped instruments which allow us to“see.”What exactly this business of“seeing”is, I do not know.And for the moment it interests me no more than the fact that the color red is produced by 392,000,000,000 impulses per second on the retina while violet demands double that amount, or 757,000,000,000 impulses per second.

Nor do I want to discuss the allegation of certain famous physicians that the human eye is one of the most awkward of nature's many clumsy devices and that almost any first-rate manufacturer of optical instruments would have been able to give us something infinitely better and more serviceable.

Such little bits of scientific gossip are interesting(if true),but they lie outside of the realm of the present volume and shall receive no further attention.

Behold. therefore, our earliest ancestor gazing into space and in a vague and none-too-certain way wondering what it is all about.

He knew, of course, what his eyes were for. They allowed him to observe those objects that were within a comparatively short distance of his eyes.

He must have realized that the“power of observation and discernment”was located in the two round balls situated on both sides of the opening by means of which he was able to smell the track of wild animals, and right above the slit through which he could fill himself with food and which enabled him to utter those cries of warning which in than of danger allowed him to communicate his own fears to his friends.

What this power of observation was, he probably knew no better than we do, half a million years later. But that it must be situated in those two round balls in the front of the head was certain, since the closing of the eyelids made a temporary end to all“seeing”and since those whose faces had been clawed by a tiger or a bear were so completely helpless that they had to be killed lest they make a nuisance of themselves and endanger the safety of the rest of the tribe.

One other thing must have penetrated to his consciousness:those two little round balls right above his mouth mad his nose lost all usefulness the moment the sun had disappeared beyond the distant horizon.

It seemed that certain other animals were able to see even when it was dark, but the species to which man belonged did not enjoy that advantage. Hence when the day came to an end, human beings were forced to retire to their nests or their caves or wherever they happened to sleep and there await the first rays of the next morning.

As soon, however, as it trod been discovered that one could not only keep a fire going that had been taken from a burning bush. but also that one could make fire by artificial means, the night lost a good many of its terrors.Thereafter the human eye was able to fortify itself with a substitute for the light of day in the form of a torch.But the torch was not an ideal instrument of illumination.It was a very important invention, but it was only a beginning.One after another, all the different materials that were in the least inflammable were used for purposes of illumination, but very little progress was made until it was discovered that one could put some fibrous material in a bowl of oil or grease and keep it burning as long as the oil or the grease lasted.

In that way the“lampas”or“torch”of the Greeks became the lamp of the modern world.

The heroes of Homer still feasted by the flickering flames of torches. But four hundred years later the temples of the gods were made resplendent with the soft radiance of innumerable small oil lamps and a century afterwards the oil lamp had become an integral part of every well-appointed household and far underneath the ground, miserable slaves, chained to the side of the mine walls, were hacking away at the coal and copper by the uncertain light of portable lamps made out of lead or iron.

For almost a thousand years smoky and smelly oil lamps were all we had for purposes of illumination. Then the lamp began to change its shape and slowly grew into the candle, which is really a lamp in which the oil has been discarded for tallow, but in which the wick has been retained as before.

During the twelfth century the artificial“glowers”found their way across the Alps and by the middle of the thirteenth century they had come into general use. And thereafter they maintained themselves as the exclusive auxiliaries for the eye-in-the-dark for several hundred years.

During this time many experiments were made with substitutes for the traditional tallow, but the only material that would serve the purpose was beeswax, and as beeswax was very expensive, these candles were never found outside of churches and palaces.

Even there they could dispel only a few square yards of darkness, mad when the living conditions of the masses began to improve and more and more people desired to keel awake a few hours after their horses and cows, there arose a demand for a better way of fighting the discomforts of night.

The problem was finally solved by tapping that same reservoir of prehistoric energy which just then was beginning to set the wheels of a million engines going, but in a somewhat different fashion. The existence of certain invisible substances which had neither volume nor shape was perfectly well known to the Greek physicists who lived twenty-five centuries ago.But they regarded them with grave suspicion, as mysterious forces capable of great harm and small good and did not inquire whether they could be used for any practical purposes.

To the alchemists of the Middle Ages, this pneuma or aura or spiritus or whatever they liked to call it came as a veritable blessing. The queer flames they produced were of great assistance in wheedling money out of recalcitrant customers and one old sinner specialized so successfully in the manufacture of“emanations”that quite by accident he happened upon the substance which nowadays we know as carbon dioxide, but which impressed him so deeply that he favored it with a new and imposing name, derived from no lesser source than the Greek word“chaos”and called it“gas”.

The name stuck, although van Helmont himself has long since been forgotten. To-day, however, when we say“gas”we usually mean the particular gas which is distilled from coal and is used for illuminating purposes, The burning propensities of coalgas had been noticed as long ago as the seventeenth century.But the man who was responsible for that invention was ahead of his time.Pigs'bladders filled with gas and used for trick lighting stunts remained part of the side-shows of country fairs, but the average man continued to be dreadfully afraid of the dangerous effluvium which was supposed to pour out of a crack of Hades and would not have it in his house, lest he be suffocated in his own bed.

During the wars of the French Revolution, when balloons suddenly gained great military, virtue, a Belgian physicist tried the experiment of filling the large paper bags with gas. instead of hot air, and having manufactured more of the stuff than he needed for aeronautical purposes, he used the surplus to light up his own apartment.People looked at this effort to turn the night into day with distinct disapproval and it was not until well after the Napoleonic wars that coal-gas began to be used in a general way for the purpose of illuminating houses and public thoroughfares.Even then thousands of people were bitterly opposed to this innovation and they found cordial supporters among the ecclesiastical authorities.

These worthy divines offered a variety of reasons for their disapprobation of the new lighting system. As a rule they based their interdicts upon that chapter in Genesis which explains how God made both the day and the night.From this they concluded that all efforts to improve upon God's handiwork by giving the eye a chance to see with perfect clarity after sundown were blasphemous expressions of human arrogance.

But the most brilliant excuse for keeping the lamplighter off his streets was given by the ruler of the good city of Cologne, who declared that the use of gas was not only unchristian but also unpatriotic. For people, so he reasoned, who lived in gaslit towns would no longer be impressed by festive illuminations, and festive illuminations were an everlasting source of inspiration for an exalted form of patriotism and respect for the reigning dynasty.

To-day all this sounds quite absurd. Gas as a substitute for the light of day has been adopted by all the world.It reigned supreme until some one invented a way of changing coal into electric energy.Since then a single citizen, bright enough to throw a couple of switches, can light up an entire city.

At last the human eye had been set free from the curse of darkness. And people did what they will always do when they are suddenly given a great deal of liberty.They began to abuse their new freedom in a scandalous fashion.Eyes that had been given them that they might be used for seven or eight hours of the day were forced to read all through the night.The poor things could not stand the strain and soon began to show signs of wear and tear.It was necessary to renforce them for those who were obliged to read or write for the greater part of every twenty-four hours.The difficulty was solved by the introduction of“spectacles”or“glasses.”

Roger Bacon is usually named as their inventor, He may have been or not. We don't know.Bacon was one of the few independent minds of the thirteenth century, and as such got blamed for almost everything new that appeared above the horizon between the years 1214 and 1294.And anyway for a long time glasses were of very little practical use, as they were regarded primarily as a luxury and not as a necessity and therefore were a hindrance quite as often as a help.Yet thousands of people used them.For there is in every one of us a streak of vanity.During a period when ninety-five per cent of all the people could neither read nor write, it was quite a swanky thing to embellish one's nose with glasses.They proclaimed to the poor devils who were too poor to buy them:“Behold!I have spent so much time upon my studies that my eyesight has suffered from too close application to learning.”

This widespread snobbishness caused an equally widespread prejudice against glasses and it lasted until very recently. The substitute eyes made out of polished crystal were derided as an affectation unworthy of real men.As Heinrich Heine discovered when he called upon the oracle of Weimar and was told that he could not appear within the presence of the great and glorious Goethe without first removing his specs.

And now to more serious business, for we have not yet mentioned the very important efforts that have been made by man to multiply his power of vision in such a way that he should be able to cast his glance into the most hidden and inaccessible secrets of nature.

Electricity gave him opportunity to devise a long-distance eye called a searchlight, which permitted him to examine the sea or the air during the night as wall as during the day. But searchlights are too intimately connected with warfare to be of any special use in time of peace.There are two other varieties of the multiplied eye which are of much greater usefulness.

There were the heavens. Man, a humble prisoner on a small planet, has always been profoundly curious about the objects that surrounded his own domicile.

But in the beginning the eyes were all he had with which to study the stars. To judge by their achievements as astronomers, the Babylonians and the Egyptians and the Greeks seem either to have enjoyed excellent eyesight, or to have been possessed of a highly developed sense of observation.What they saw, they saw correctly, but their range of vision was necessarily limited.For they were obliged to rely upon the human eye unassisted by any of those artificial multiplications of the power of vision which are to-day at our disposal.

The learned Roger Bacon not only seems to have discovered our spectacles;he also described a method by which one could construct a“far-seer”or telescope. Whether he ever made such an instrument for his own amusement is uncertain.He was a busy, man, and during the many years he was not allowed to put pen to paper he was as a rule much too poor to indulge in expensive optical experiments.

Anyway, nothing was done about the telescope until four hundred years after his death. Then the fury of the Reformation had at last spent itself and for a short while people could indulge their desire for scientific speculations.At the same time little ships were beginning to sail across every inlet and bay of the Seven Seas and their mariners were in great need of an instrument that should allow them to see-at-a-distance.Small wonder, therefore, that the telescope was invented by inhabitants of the Low Countries, where navigation had been elevated to the rank of a line art.

From Holland telescopes were exported to every part of Europe. One of them fell into the hands of Galileo and the purpose for which he used it justified the decree of the general of the Franciscans when he had forbidden Roger Bacon to continue his dangerous studies in the realm of applied physics.For Galileo, with a far-seer of his own fabrication(a childish enough instrument when we compare it to one of our modem telescopes),enlarged the dome of heaven by so many thousands of miles that all the old notions about the importance of the Earth and its sister-planets and its fiery little Sun were completely upset, and that the whole of the universe came in for a thorough house-cleaning.

Rather than revise the comfortable opinion which they had held since the year one, the majority of the people preferred to call Galileo and his fellow astronomers dangerous radicals and perfidious fellows who should be prevented from teaching their outrageous doctrines to the younger generation.

In the end, as always, man's divine curiosity triumphed. He continued to increase his range of vision until to-day with the help of gigantic telescopes he is at last beginning to get a faint idea, not of where he is but at least of whither he is going.

Now while certain people were devoting themselves to the problem of seeing extensively, others were trying to discover a way of seeing intensively. For as soon as it had become dear that there was a world which existed outside of our range of observation, because it was situated so far away that it could not possibly be sensed by the naked eye, it was suspected that there might also be a world composed of creatures so infinitely small that they could not possibly be noticed without the assistance of a differently multiplied power of vision.

The Greeks were the first to have suspicions in this general direction. Without lenses of the proper sort, those suspicions could not be revaluated into actual knowledge.

The most the ancients could do to magnify the human eye was to look at an object through a hollow sphere filled with water, and that was little enough.

But once lenses had been invented, people were on the right track. Four hundred years were spent in making experiments and then, during the first half of the seventeenth century, some one in Holland by the name of van Leeuwenhoek combined a few lenses in such a way that at last the human eye was able to detect the little organisms whose existence had been predicted thousands of years before.

The new instrument was aptly called a microscope or a“smallseer.”The first microscopes were painfully primitive but they were rapidly improved, and half a century ago we at last made the acquaintance of some of our worst enemies—the microbes. Not all of them, for even after the introduction of the most powerful microscopes, several of the nefarious tribe have managed to keep themselves hidden from our gaze.

In a world in which we have learned to look“through”people with the help of Professor Rocntgen's extraordinary invention, almost anything seems possible and most of the problems of existence become reduced to two simple words:“Courage!”and“Patience.”

And that is all for the moment.

For my pictures have come to an end, and as Alice said quite rightly:“What is the use of a book without pictures?”

If I had had time and if printing were not so terribly expensive, it would have been easy to multiply my examples of the multiplication of the human organs until this book should have contained three thousand pages instead of less than three hundred. For I have merely touched upon a few of the high spots.The details have not even been mentioned.

Even now, the reader, if he has had sufficient courage to peruse this volume to the end, has probably said to himself:“Why did the ignorant fellow forget this?Why did he omit that?Why didn't he mention the stairs as an extension of the foot when he was discussing the road?Isn't a gimlet a multiplication of the powers of the hand?What about armor as an extra layer of skin?What about bloodhounds as a substitute for the human nose?”

And he would be right. Hundreds of other subjects could have been mentioned but this book does not pretend to be a“History of Invention”or a collection of essays upon the unhappy lives of most of the pioneers of human intelligence.

On the contrary, it is merely an intellectual eye-opener.

Its purpose is to give the average reader a new point of view and to provide him with a short and workable outline which will enable him to do his own classifying hereafter by himself and get some amusement(and perhaps instruction)out of the perfectly harmless sport of dividing and subdividing all existing inventions.

But there is something else I have tried to do.

As I said in my foreword, the present book is really a confession of faith. The hammers and saws and balloons and telescopes were merely an excuse for saying a few things which are apt to be overlooked in this age of pessimism and spiritual despondency.

The underlying philosophy of the present volume is one of hope and optimism.

It shows us Man, not as a victim of fate, but as a creature endowed with practically unlimited powers for the development of his brain. It shows us Man still at the beginning of his career as a reasonable being, but rapidly discovering by which road be may eventually hope to escape from those difficulties which make his present existence such a torture.

I know that people will object and will say that salvation must eventually come through the spirit Quite true!But the spirit has a poor time of it when the body has got to dig for potatoes in order to keep alive.

Thus far Man has wasted too much of his time digging potatoes.

I want him to stop digging that he may have leisure to develop his higher faculties.

What use he will make of those higher faculties, we, who belong to the late Stone Age, are not able to prophesy, but the evidence of the past encourages us to expect that he will do better and better as he relieves himself more and more from that drudgery which so often has threatened to degrade him to the order of the bees and ants.

The present moment is in many respects an unfortunate one. Just now we are neither slave nor master.We multiplied the powers of our hands and our feet and our eyes and our ears that we might achieve liberty and suddenly we found ourselves at the mercy of those inanimate beings who had been created to serve us.

That, however, does not mean that we should never have tried to multiply our faculties.

It merely shows that we have not yet multiplied them enough.

That is the task which awaits us.