Boys' Second Book of Inventions

The solar motor is expected to operate at all seasons of the year, regardless of all climatic conditions, with the single exception of cloudy skies. Cold makes no difference whatever. The best results from the first model used in experimental work at Denver were obtained at a time when the pond from which the water was pumped was covered with a thick coating of ice. But, of course, the length of the solar day is longer in the summer, giving more heat and more power. The motor may be depended upon for work from about one hour and a half after sunrise to within half an hour of sunset. In the summer time this would mean about twelve hours' constant pumping.

Think what such an invention means, if practically successful, to the vast stretches of our arid Western land, valueless without water. Spread all over this country of Arizona, New Mexico, Southern California, and other States are thousands of miles of canals to bring in water from the rivers for irrigating the deserts, and there are untold numbers of wind-mills, steam and gasoline pumps which accomplish the same purpose more laboriously. Think what a new source of cheap power will do – making valuable hundreds of acres of desert land, providing homes for thousands of busy Americans. Indeed, a practical solar motor might make habitable even the Sahara Desert. And it can be used in many other ways besides for pumping water. Threshing machines might be run by this power, and, converted into electricity and saved up in storage batteries, it might be used for lighting houses, even for cooking dinners, or in fact for any purpose requiring power.

These solar motors can be built at no great expense. I was told that ten-horse-power plants would cost about $200 per horse-power, and one-hundred-horse-power plants about $100 per horse-power. This would include the entire plant, with engine and pump complete. When it is considered that the annual rental of electric power is frequently $50 per horse-power, whether it is used or not, it will be seen that the solar motor means a great deal, especially in connection with irrigation enterprises.

And the time is coming – long-headed inventors saw it many years ago – when some device for the direct utilisation of the sun's heat will be a necessity. The world is now using its coal at a very rapid rate; its wood, for fuel purposes, has already nearly disappeared, so that, within a century or two, new ways of furnishing heat and power must be devised or the human race will perish of cold and hunger. Fortunately there are other sources of power at hand; the waterfalls, the Niagaras, which, converted into electricity, may yet heat our sitting-rooms and cook our dinners. There is also wind-power, now used to a limited extent by means of wind-mills. But greater than either of these sources is the unlimited potentiality of the tides of the sea, which men have sought in vain to harness, and the direct heat of the sun itself. Some time in the future these will be subdued to the purpose of men, perhaps our main dependence for heat and power.

When we come to think of it, the harnessing of the sun is not so very strange. In fact, we have had the sun harnessed since the dawn of man on the earth, only indirectly. Without the sun there would be nothing here – no men, no life. Coal is nothing but stored-up, bottled sunshine. The sunlight of a million years ago produced forests, which, falling, were buried in the earth and changed into coal. So when we put coal in the cook-stove we may truthfully say that we are boiling the kettle with million-year-old sunshine. Similarly there would be no waterfalls for us to chain and convert into electricity, as we have chained Niagara, if the sun did not evaporate the waters of the sea, take it up in clouds, and afterward empty the clouds in rain on the mountain-tops from whence the water tumbles down again to the sea. So no wind would blow without the sun to work changes in the air.

In short, therefore, we have been using the sunlight all these years, hardly knowing it, but not directly. And think of the tremendous amount of heat which comes to the earth from the sun. Every boy has tried using a burning-glass, which, focusing a few inches of the sun's rays, will set fire to paper or cloth.

Professor Langley says that "the heat which the sun, when near the zenith, radiates upon the deck of a steamship would suffice, could it be turned into work without loss, to drive her at a fair rate of speed."

The knowledge of this enormous power going to waste daily and hourly has inspired many inventors to work on the problem of the solar motor. Among the greatest of these was the famous Swedish engineer, John Ericsson, who invented the iron-clad Monitor. He constructed a really workable solar motor, different in construction but similar in principle to the one in California which I have described. In 1876 Ericsson said:

"Upon one square mile, using only one-half of the surface and devoting the rest to buildings, roads, etc., we can drive 64,800 steam-engines, each of 100 horse-power, simply by the heat radiating from the sun. Archimedes, having completed his calculation of the force of a lever, said that he could move the earth. I affirm that the concentration of the heat radiated by the sun would produce a force capable of stopping the earth in its course."

A firm believer in the truth of his theories, he devoted the last fifteen years of his life and $100,000 to experimental work on his solar engine. For various reasons Ericsson's invention was not a practical success; but now that modern inventors, with their advancing knowledge of mechanics, have turned their attention to the problem, and now that the need of the solar motor is greater than ever before, especially in the world's deserts, we may look to see a practical and successful machine. Perhaps the California motor may prove the solution of the problem; perhaps it will need improvements, which use and experience will indicate; perhaps it may be left for a reader of these words to discover the great secret and make his fortune.

CHAPTER VI

THE INVENTOR AND THE FOOD PROBLEM

Fixing of Nitrogen – Experiments of Professor Nobbe

No lad of to-day, ambitious to become a scientist or inventor, reading of all the wonderful and revolutionising discoveries and inventions of recent years, need fear for plenty of new problems to solve in the future. No, the great problems have not all been solved. We have the steam-engine, the electric motor, the telegraph, the telephone, the air-ship, but not one of them is perfect, not one that does not bring to the attention of inventors scores of entirely new problems for solution. The further we advance in science and mechanics the further we see into the marvels of our wonderful earth and of our life, and the more there is for us to do.

As population increases and people become more intelligent there is a constant demand for new things, new machinery which will enable the human race to move more rapidly and crowd more work and more pleasure into our short human life. One man working to-day with machinery can accomplish as much as many men of a hundred years ago; he can live in a house that would then have been a palace; enjoy advantages of education, amusement, luxury, that would then have been possible only to kings and princes.

And the very greatest of all the problems which the inventors and scientists of coming generations must solve is the question – seemingly commonplace – of food.

We who live in this age of plenty can hardly realise that food could ever be a problem. But far-sighted scientists have already begun to look forward to the time when there will be so many people on the earth that the farms and fields will not supply food for every one. It is a well-known fact that the population of the world is increasing enormously. Think how America has been expanding; a whole continent overrun and settled almost within a century and a half! Nearly all the land that can be successfully farmed has already been taken up, and the land in some of the older settled localities, like Virginia and the New England States, has been so steadily cropped that it is failing in fertility, so that it will not raise as much as it would years ago. In Europe no crop at all can be raised without quantities of fertiliser.

While there was yet new country to open up, while America and Australia were yet virgin soil, there was no immediate cause for alarm; but, as no less an authority than Sir William Crookes pointed out a few years ago in a lecture before the British Association, the new land has now for the most part been opened and tamed to the plough or utilised for grazing purposes. And already we are hearing of worn-out land in Dakota – the paradise of the wheat producer. The problem, therefore, is simple enough: the world is reaching the limits of its capacity for food production, while the population continues to increase enormously: how soon will starvation begin? Sir William Crookes has prophesied, I believe, that the acute stage of the problem will be reached within the next fifty years, a time when the call of the world for food cannot be supplied. If it were not for our coming inventors and scientists it would certainly be a gloomy outlook for the human race.

But science has already foreseen this problem. When Sir William Crookes gave his address he based his arguments on modern agricultural methods; he did not look forward into the future, he did not show any faith in the scientists and inventors who are to come, who are now boys, perhaps. He did not even take cognisance of the work that had already been done. For inventors and scientists are already grappling with this problem of food.

In a nutshell, the question of food production is a question of nitrogen.

This must be explained. A crop of wheat, for instance, takes from the soil certain elements to help make up the wheat berry, the straw, the roots. And the most important of all the elements it takes is nitrogen. When we eat bread we take this nitrogen that the wheat has gathered from the soil into our own bodies to build up our bones, muscles, brains. Each wheat crop takes more nitrogen from the soil, and finally, if this nitrogen is not given back to the earth in some way, wheat will no longer grow in the fields. In other words, we say the farm is "worn out," "cropped to death." The soil is there, but the precious life-giving nitrogen is gone. And so it becomes necessary every year to put back the nitrogen and the other elements which the crop takes from the soil. This purpose is accomplished by the use of fertilisers. Manure, ground bone, nitrates, guano, are put in fields to restore the nitrogen and other plant foods. In short, we are compelled to feed the soil that the soil may feed the wheat, that the wheat may feed us. You will see that it is a complete circle – like all life.

Now, the trouble, the great problem, lies right here: in the difficulty of obtaining a sufficient amount of fertiliser – in other words, in getting food enough to keep the soil from nitrogen starvation. Already we ship guano – the droppings of sea-birds – from South America and the far islands of the sea to put on our lands, and we mine nitrates (which contain nitrogen) at large expense and in great quantities for the same purpose. And while we go to such lengths to get nitrogen we are wasting it every year in enormous quantities. Gunpowder and explosives are most made up of nitrogen – saltpetre and nitro-glycerin – so that every war wastes vast quantities of this precious substance. Every discharge of a 13-inch gun liberates enough nitrogen to raise many bushels of wheat. Thus we see another reason for the disarmament of the nations.

A prediction has been made that barely thirty years hence the wheat required to feed the world will be 3,260,000,000 bushels annually, and that to raise this about 12,000,000 tons of nitrate of soda yearly for the area under cultivation will be needed over and above the 1,250,000 tons now used by mankind. But the nitrates now in sight and available are estimated good for only another fifty years, even at the present low rate of consumption. Hence, even if famine does not immediately impend, the food problem is far more serious than is generally supposed.

Now nitrogen, it will be seen, is one of the most precious and necessary of all substances to human life, and it is one of the most common. If the world ever starves for the lack of nitrogen it will starve in a very world of nitrogen. For there is not one of the elements more common than nitrogen, not one present around us in larger quantities. Four-fifths of every breath of air we breathe is pure nitrogen – four-fifths of all the earth's atmosphere is nitrogen.

But, unfortunately, most plants are unable to take up nitrogen in its gaseous form as it appears in the air. It must be combined with hydrogen in the form of ammonia or in some nitrate. Ammonia and the nitrates are, therefore, the basis of all fertilisers.

Now, the problem for the scientist and inventor takes this form: Here is the vast store-house of life-giving nitrogen in the air; how can it be caught, fixed, reduced to the purpose of men, spread on the hungry wheat-fields? The problem, therefore, is that of "fixing" the nitrogen, taking the gas out of the air and reducing it to a form in which it can be handled and used.

Two principal methods for doing this have already been devised, both of which are of fascinating interest. One of these ways, that of a clever American inventor, is purely a machinery process, the utilisation of power by means of which the nitrogen is literally sucked out of the air and combined with soda so that it produces nitrate of soda, a high-class fertiliser. The water power of Niagara Falls is used to do this work – it seems odd enough that Niagara should be used for food production!

The other method, that of a hard-working German professor, is the cunning utilisation of one of nature's marvellous processes of taking the nitrogen from the air and depositing it in the soil – for nature has its own beautiful way of doing it. I will describe the second method first because it will help to clear up the whole subject and lead up to the work of the American inventor and his extraordinary machinery.

Nearly every farmer, without knowing it, employs nature's method of fixing nitrogen every year. It is a simple process which he has learned from experience. He knows that when land is worn out by overcropping with wheat or other products which draw heavily on the earth's nitrogen supply certain crops will still grow luxuriantly upon the worn-out land, and that if these crops are left and ploughed in, the fertility of the soil will be restored, and it will again produce large yields of wheat and other nitrogen-demanding plants. These restorative crops are clover, lupin, and other leguminous plants, including beans and peas. Every one who is at all familiar with farming operations has heard of seeding down an old field to clover and then ploughing in the crop, usually in the second year.

The great importance of this bit of the wisdom of experience was not appreciated by science for many years. Then several German experimenters began to ask why clover and lupin and beans should flourish on worn-out land when other crops failed. All of these plants are especially rich in nitrogen, and yet they grew well on soil which had been robbed of its nitrogen. Why was this so?

It was a hard problem to solve, but science was undaunted. Botanists had already discovered that the roots of the leguminous plants – that is, clover, lupin, beans, peas, and so on – were usually covered with small round swellings, or tumors, to which were given the name nodules. The exact purpose of these swellings being unknown, they were set down as a condition, possibly, of disease, and no further attention was paid to them until Professor Hellriegel, of Burnburg, in Anhalt, Germany, took up the work. After much experimenting, he made the important discovery that lupins which had nodules would grow in soil devoid of nitrogen, and that lupins which had no nodules would not grow in the same soil. It was plain, therefore, that the nodules must play an important, though mysterious, part in enabling the plant to utilise the free nitrogen of the air. That was early in the '80s. His discovery at once started other investigators to work, and it was not long before the announcement came – and it came, curiously enough, at a time when Dr. Koch was making his greatest contributions to the world's knowledge of the germ theory of disease – that these nodules were the result of minute bacteria found in the soil. Professor Beyerinck, of Münster, gave the bacteria the name Radiocola.

It was at this time that Professor Nobbe took up the work with vigour. If these nodules were produced by bacteria, he argued that the bacteria must be present in the soil; and if they were not present, would it not be possible to supply them by artificial means? In other words, if soil, say worn-out farm-soil or, indeed, pure sand like that of the sea-shore could thus be inoculated, as a physician inoculates a guinea-pig with diphtheria germs, would not beans and peas planted there form nodules and draw their nourishment from the air? It was a somewhat startling idea, but all radically new ideas are startling; and, after thinking it over, Professor Nobbe began, in 1888, a series of most remarkable experiments, having as their purpose the discovery of a practical method of soil inoculation. He gathered the nodule-covered roots of beans and peas, dried and crushed them, and made an extract of them in water. Then he prepared a gelatine solution with a little sugar, asparagine, and other materials, and added the nodule-extract. In this medium colonies of bacteria at once began to grow – bacteria of many kinds. Professor Nobbe separated the Radiocola – which are oblong in shape – and made what is known as a "clear culture," that is, a culture in gelatine, consisting of billions of these particular germs, and no others. When he had succeeded in producing these clear cultures he was ready for his actual experiments in growing plants. He took a quantity of pure sand, and, in order to be sure that it contained no nitrogen or bacteria in any form, he heated it at a high temperature three different times for six hours, thereby completely sterilising it. This sand he placed in three jars. To each of these he added a small quantity of mineral food – the required phosphorus, potassium, iron, sulphur, and so on. To the first he supplied no nitrogen at all in any form; the second he fertilised with saltpetre, which is largely composed of nitrogen in a form in which plants may readily absorb it through their roots; the third of the jars he inoculated with some of his bacteria culture. Then he planted beans in all three jars, and awaited the results, as may be imagined, somewhat anxiously. Perfectly pure sterilised water was supplied to each jar in equal amounts and the seeds sprouted, and for a week the young shoots in the three jars were almost identical in appearance. But soon after that there was a gradual but striking change. The beans in the first jar, having no nitrogen and no inoculation, turned pale and refused to grow, finally dying down completely, starved for want of nitrogenous food, exactly as a man would starve for the lack of the same kind of nourishment. The beans in the second jar, with the fertilised soil, grew about as they would in the garden, all of the nourishment having been artificially supplied. But the third jar, which had been jealously watched, showed really a miracle of growth. It must be remembered that the soil in this jar was as absolutely free of nitrogen as the soil in the first jar, and yet the beans flourished greatly, and when some of the plants were analysed they were found to be rich in nitrogen. Nodules had formed on the roots of the beans in the third or inoculated jar only, thereby proving beyond the hope of the experimenter that soil inoculation was a possibility, at least in the laboratory.

With this favourable beginning Professor Nobbe went forward with his experiments with renewed vigour. He tried inoculating the soil for peas, clover, lupin, vetch, acacia, robinia, and so on, and in every case the roots formed nodules, and although there was absolutely no nitrogen in the soil, the plants invariably flourished. Then Professor Nobbe tried great numbers of difficult test experiments, such as inoculating the soil with clover bacteria and then planting it with beans or peas, or vice versa, to see whether the bacteria from the nodules of any one leguminous plant could be used for all or any of the others. He also tried successive cultures; that is, bean bacteria for beans for several years, to see if better results could be obtained by continued use. Even an outline description of all the experiments which Professor Nobbe made in the course of these investigations would fill a small volume, and it will be best to set down here only his general conclusions.

These wonderful nitrogen-absorbing bacteria do not appear in all soil, although they are very widely distributed. So far as known they form nodules only on the roots of a few species of plants. In their original form in the soil they are neutral – that is, not especially adapted to beans, or peas, or any one particular kind of crop. But if clover, for instance, is planted, they straightway form nodules and become especially adapted to the clover plant, so that, as every farmer knows, the second crop of clover on worn-out land is much better than the first. And, curiously enough, when once the bacteria have become thoroughly adapted to one of the crops, say beans, they will not affect peas or clover, or only feebly.

Another strange feature of the life of these little creatures, which has a marvellous suggestion of intelligence, is their activities in various kinds of soil. When the ground is very rich – that is, when it contains plenty of nitrogenous matter – they are what Professor Nobbe calls "lazy." They do not readily form nodules on the roots of the plants, seeming almost to know that there is no necessity for it. But when once the nitrogenous matter in the soil begins to fail, then they work more sharply, and when it has gone altogether they are at the very height of activity. Consequently, unless the soil is really worn out, or very poor to begin with, there is no use in inoculating it – it would be like "taking owls to Athens," as Professor Nobbe says.

Having thus proved the remarkable efficacy of soil inoculation in his laboratory and greenhouses, where I saw great numbers of experiments still going forward, Professor Nobbe set himself to make his discoveries of practical value. He gave to his bacteria cultures the name "Nitragen" – spelled with an "a" – and he produced separate cultures for each of the important crops – peas, beans, vetch, lupin, and clover. In 1894 the first of these were placed on the market, and they have had a steadily increasing sale, although such a radical innovation as this, so far out of the ordinary run of agricultural operation, and so almost unbelievably wonderful, cannot be expected to spread very rapidly. The cultures are now manufactured at one of the great commercial chemical laboratories on the river Main. I saw some of them in Professor Nobbe's laboratory. They come in small glass bottles, each marked with the name of the crop for which it is especially adapted. The bottle is partly filled with the yellow gelatinous substance in which the bacteria grow. On the surface of this there is a mossy-like growth, resembling mould. This consists of innumerable millions of the little oblong bacteria. A bottle costs about fifty cents and contains enough bacteria for inoculating half an acre of land. It must be used within a certain number of weeks after it is obtained, while it is still fresh. The method of applying it is very simple. The contents of the bottle are diluted with warm water. Then the seeds of the beans, clover, or peas, which have previously been mixed with a little soil, are treated with this solution and thoroughly mixed with the soil. After that the mass is partially dried so that the seeds may be readily sown. The bacteria at once begin to propagate in the soil, which is their natural home, and by the time the beans or peas have put out roots they are present in vast numbers and ready to begin the active work of forming nodules. It is not known exactly how the bacteria absorb the free nitrogen from the air, but they do it successfully, and that is the main thing. Many German farmers have tried Nitragen. One, who was sceptical of its virtues, wrote to Professor Nobbe that he sowed the bacteria-inoculated seeds in the form of a huge letter N in the midst of his field, planting the rest in the ordinary way. Before a month had passed that N showed up green and big over all the field, the plants composing it being so much larger and healthier than those around it.