Popular Science Monthly/Volume 51/July 1897/Forecasting the Progress of Invention

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THE great progress made during the last fifty years in the domain of science and invention has aroused a very general desire among intelligent people to know what the future has in store, and in many cases the desire has become so strong as to develop prophetic tendencies. Whenever a banquet is given in commemoration of some scientific event, or upon the anniversary of some ancient and honorable society, the orator of the evening is sure to dwell at considerable length upon the great discoveries that are still to come. By contrasting the extraordinary advances made during the last century with the comparatively limited progress of all previous time, and by showing that the rate of advancement has been continually increasing during the latter period, he arrives at the conclusion that in the years to come development will increase in a compound ratio, and the discoveries will become so numerous and so great as to dwarf into insignificance all that has been accomplished up to the present time.

Writers who dwell upon these glorious achievements of mankind in modern times follow the same vein, and make equally extravagant predictions as to the future. If these writers and orators would stop when they reach this point in their meditations they would be wise, since it is a self-evident fact that progress in science and invention has been increasing very rapidly during the last fifty or sixty years, and certainly there is no reason to suppose that we have reached the end, and that henceforth development will be very slow; but at this point the spirit of prophecy seizes them, and they proceed to describe the wonders yet unseen. It is here that they almost invariably fail. They would not be satisfied if they assumed that future progress would be along the lines of possible development—that would be too commonplace and altogether out of keeping with the ideal of the greatness of the future achievements of mankind. They must necessarily assume that what is brought forth hereafter will be so far in advance of what we now know of as to be revolutionary in its character, and so much so, in fact, as to consign to the scrap heap the most perfect devices of the present time. Some of the means by which these results are to be attained are not capable of accomplishing such wonders; others, while of great theoretical possibilities, are surrounded by certain practical difficulties so well understood at the present time that we can almost with certainty say that they will never realize the dreams that are based upon them. The remainder are problems that can be solved to-day, and would be if it were not for the fact that it is by no means certain that their solution would be of any practical value. The improbability of ever realizing a substantial gain by the solution of many of the problems upon which prophecies as to the wonders of the future are based is fully appreciated by many of those who have given the subject careful consideration; but those who dream of the revolutionary character of future invention never take note of such things.

Nearly all those who succumb to the fascination of meditating upon the changes that may be wrought by inventive genius in days to come follow the same line of thought. The problems upon the solution of which their fancy paints its pictures are always the same, although some contemplate the whole category, while others only dwell upon a portion thereof. These problems are aerial navigation, the development of electric energy direct from coal or some other equally cheap substance, and the utilization of the various forces of Nature, such as solar heat, tide and wave motion, and wind currents. Of these, aerial navigation is supposed to be by far the most important, obtaining electricity direct from coal and the others following along in the order in which they are given above.

As to the utilization of solar heat, tides, wave motion, and wind currents, it can be truthfully said that they could be utilized at the present time if it were considered profitable to do so. The energy of wind currents, as every one knows, is made available on a very extensive scale, but always in small units, and this fact alone shows that it can not compete with the steam engine, which, according to the prophets, it is sure to supersede. The energy of tides and wave motion is also utilized to some extent, and solar engines have been made from time to time.

It can not be said that these unlimited sources of energy are not brought into the service of man because of our inability to devise apparatus with which to harness them successfully, for, as a matter of fact, a great deal of ingenuity has been displayed in this direction, and the cost of the mechanism, with reference to the power recovered, has probably been reduced to nearly as low a point as is possible. In the matter of simplicity and durability equally good results have been obtained.

An analysis of the most salient features of these forms of energy will show why they are not utilized on a more extensive scale. The power of waves and tides is only available along the seacoast, where, as a rule, power is not in demand; furthermore, any kind of apparatus made to utilize this energy must be very strong and bulky in comparison with the power it will give, and as a consequence very costly. In addition to this, the amount of energy will vary greatly at different seasons; hence the output that can be depended upon at all times must be far below the actual capacity of the apparatus. A further drawback is the great irregularity of the power, which renders it of little value unless means are provided for reducing it to a delivery at a uniform rate.

Windmills are not so much restricted, as to location, as the foregoing, but they are very large in comparison to the work they can do, and, as the velocity of the wind may drop to nearly zero for a long period of time, their average capacity, taking the year through, may be exceedingly small.

Solar energy is available everywhere, but the capacity of an apparatus made to utilize it would be very indefinite and far below its maximum, owing to the fact that cloudy weather may come at any time and continue for days or even weeks.

The irregularity of the power derived from these sources can be overcome by resorting to some form of storage, but this would not help, except to a limited extent, to increase the average output; therefore, when the apparatus was working at its full capacity, there would be a large surplus of power going to waste. By increasing the capacity of the storage reservoirs, the average output could be increased, and if the intervals of time during which the energy developed is little or nothing were short, say two or three days, and were followed by corresponding intervals of maximum output, it would probably be profitable to make the capacity great enough to store all the surplus developed at times of maximum output; but, as these periods may each extend over two or three weeks, it is evident that about the best we can do is to increase the average output slightly by using a greater storage capacity.

As these natural forms of energy can be obtained without cost, and the fuel used by a steam engine has to be purchased, it is apparently reasonable to assume that they would constitute a more economical form of power, but wherever a constant supply is desired it is very doubtful whether the economy of the steam engine can be superseded by any one of them. It is true that there is no expenditure for fuel, but the interest on the extra cost of the plant and the maintenance thereof, as well as the additional space required, may more than offset this gain; and the fact that so little is done in the way of utilizing them would seem to show that up to the present time their value has failed to make any great impression upon engineers who have looked into the subject. It does not follow from this that they will never come into use on a more extensive scale than at present, but it does follow that the dreams of those who believe that they will eventually supersede all forms of prime movers that consume fuel will never be realized. Through the increased value of fuel or the reduced cost of construction of the apparatus, or both, they may become competitors to a greater or less extent, but more than this can not be expected.

Considering, now, the effects of the solution of the problem of obtaining electricity direct from coal, it can be said that it is far more likely to revolutionize the affairs of the world than the utilization of the natural forms of energy; but it must also be said that we are not justified, in view of what is now known in relation to the subject, in assuming that it will ever realize the predictions of the oversanguine prophets. If we could solve the problem according to our ideal, all that is expected of it would be accomplished; but such a solution is highly improbable, if not actually impossible. Our ideal battery would be as simple as a boiler, and be provided with a place where coal could be fed in and another through which the residue could be removed. In a boiler, the pressure of the steam, as well as the quantity generated, can be increased by simply increasing the size of the fire box, but this simplicity could not be obtained even in our ideal battery, because the electromotive force would remain the same no matter how much the size of the cell might be increased. To obtain an electromotive force high enough for practical purposes it would be necessary to use a large number of cells, and, to feed these without too much trouble, it would be necessary to devise an automatic feeder capable of operating with a degree of perfection hardly obtainable without the aid of human intelligence.

It may be permissible to dream of such perfection, but we are not justified in assuming that it is possible. Electricity can be obtained from chemical action only when the material acted upon is in the electric circuit. If two metals are placed in a solution that can decompose one of them, an electric current will flow in a wire the ends of which are attached to the two metals. If two solutions capable of acting upon each other are separated by a porous partition, and into each a plate attached to a wire is immersed, a current will flow. If in a solution two metals that are not acted upon are immersed, a current will not flow in a wire connecting them. If into this solution pieces of metal or other substances that will be acted upon are dropped, no current will be generated, because the chemical action takes place between substances one of which is not in the electric chain. Coal is not a conductor of electricity, in the practical sense; therefore it can not be used directly in the electric circuit, even if we could find a way to oxidize it satisfactorily; hence the only probable way of solving the coal-battery problem is by some indirect process, and this may introduce complications great enough to entirely offset all the advantages.

The belief that great development will be made along the lines discussed in the foregoing is confined to those who possess some familiarity with scientific matters, but the general run of intelligent people only have a vague idea of what may be expected from these sources, and the pictures drawn by their imagination in relation thereto are decidedly hazy; with them the greatest of all future achievements is the solution of the problem of aërial navigation. This belief is undoubtedly due to the fact that the theoretical limitations are not understood, or are not taken into consideration, and as a consequence the average conception of a perfect air ship, as well as its movements and velocity, is very different from the actual possibilities.

The most striking difference between imagination and possibility, in this line, is perhaps in the relation between the size of the ship and its carrying capacity, the latter being always greatly magnified. An examination of any considerable number of the illustrations of flying machines would show this point very forcibly. In many of these pictures the force of gravity is treated with the utmost contempt, the ship being made apparently of sheet iron, very similar in shape to a submarine torpedo boat, the sustaining power being obtained by means of one or more moderate-sized propellers mounted upon vertical shafts, or else equally small aëroplanes. In those designs that display a greater regard for the laws of Nature, the disparity in the proportions is not so great, but in all of them it is very decided.

It is evident that with our present knowledge of science there are only two ways in which an air ship can be kept afloat, one by the use of a balloon and the other by means of aëroplanes. In the former the sustaining capacity is small relatively to the volume, being about one pound for every fourteen cubic feet; and with the latter it is small relatively to the surface, being probably not over one pound to the square foot. From this it can easily be seen that the carrying capacity, even of a craft of large dimensions, must be small, very much smaller than the popular notion would make it. The sketch presented herewith will give a fair idea of the difference between reality and the general ideal, the small car shown in solid lines being large enough to carry all the passengers or freight that the balloon could sustain, and the one in dotted lines about the size generally shown in illustrations of air ships. The sketch is not above criticism, since it does not give the location of the motor or any means for revolving the propeller, but that is a peculiarity of the majority of air-ship pictures, and the writer may be pardoned for following a common custom,

PSM V51 D324 Supposed and actual carrying capacity of airships.png
Diagram showing Difference between Supposed and Actual Carrying Capacity of Air Ships.

especially as the object of the sketch is only to show the relation between size and carrying capacity.

That this sketch is not exaggerated can be easily shown. The balloon is supposed to be one hundred and twenty feet long and twenty feet in diameter, the taper at each end being forty feet. From these dimensions it will be seen that the displacement is about twenty-one thousand feet, and the sustaining capacity about fifteen hundred pounds. Now, the first thing that any conservative engineer would admit would be that the apparatus could not be constructed within this weight if the same factor of safety were used as is customary in designing any ordinary structure; hence, if any carrying capacity is to be obtained, the weight and strength of every part must be reduced to a point not regarded as permissible in ordinary practice. Following this course, we can assume the weight of the whole ship at one thousand pounds, which would certainly be light considering its size; we would then have a net carrying capacity of five hundred pounds—equal to, say, four men. The car is drawn four foot square and six feet high, which is ample for four passengers. A contemplation of the difference between the size of the balloon and the car is enough to dampen the ardor of the most enthusiastic believer in the possibilities of aerial navigation.

It may be claimed that by the use of aëroplanes the size can be considerably reduced, but this is doubtful; and if it can, it probably would not be any benefit, since, if the area of the planes is reduced, the pressure must be increased, and this would result in a less efficient application of the energy required to keep the ship in the air. Another mistaken notion that is accountable in a great measure for the belief in the wonderful possibilities of aërial navigation is that great velocity could be obtained. This assumption is entirely erroneous, and as a matter of fact it can be easily shown that higher speed can be attained on a railroad. As is perfectly well known, the principal obstacle that stands in the way of extraordinary velocity on railroads is the resistance of the atmosphere, and this would be very much greater in the case of an air ship owing to the increased size. The cross-section of a train of cars is less than one hundred and fifty feet, while that of an air ship of the same carrying capacity would probably be ten times as great if not more, and the power required to overcome atmospheric resistance would be in about the same proportion. From this it can be seen that the energy necessary to propel the ship, without saying anything about that required to keep it in the air, would be many times greater than that required to drive a train of cars at the same speed; hence, as a means of rapid transit, aërial navigation could not begin to compete with the railroad.

There is another direction in which the air ship would be seriously defective, and this is almost always overlooked, and that is in the matter of making landings. Being a large body, it would necessarily be unwieldy, and its motion in any direction could not be arrested in a very short space of time; therefore it could not make a landing within a limited area. In a dead calm it could probably be lowered in nearly a vertical line, and thus make a landing in a contracted space, but if the wind were blowing even at a moderate velocity the case would be different. As the wind is always blowing more or less, and as it frequently changes its course in a few seconds, the ship would be tossed about quite lively before it reached the ground. If it came down at the rate of three hundred feet per minute, which is a high velocity, and the wind were blowing at the rate of ten miles per hour, the side drift would be three times as great as the vertical descent; and if this were counteracted by imparting a velocity to the ship equal to that of the wind and opposed to it, the side draught would be doubled if the direction of the wind should suddenly reverse. It must therefore be evident that to be able to make a landing safely, without running the risk of colliding with church steeples and modern sky-scrapers, it would be necessary to have a large open space, and in order that the passengers might not have to walk a large portion of the length of their journey conveyances would have to be provided to transport them from the place where the ship might land to the station entrance.

It must not be assumed from what has been said in the foregoing that the writer regards the solution of the problems here considered as of no special value, for his views are just the opposite of this. The object aimed at has been to show that the wonderful things that it is expected will be accomplished by the solution of these problems will never be realized with regard to some because they are not possible, and are not likely to be realized by the others on account of inherent defects that the solutions may bring to light. The coal-battery problem will, no doubt, be worked out, in some form or other, but who can tell whether the objectionable features of it will or will not offset all its advantages? The hot-air engine is a far more perfect converter of energy, in theory, than the steam engine, but its defects when reduced to a practical form are such that it is of no value except for small power, and this may also turn out to be the case with the coal battery. The utilization of the energy of tides, solar heat, etc., is as possible to-day as at any future time; the fact that they are not utilized is proof that they are not considered as desirable as other forms of energy. In the future the cost of the apparatus for harnessing them may be so reduced as to render them available to a much greater extent than at the present time, but that they will ever revolutionize the industrial affairs of the world and drive the steam engine out of use is hardly a remote possibility. Aerial navigation will, no doubt, be accomplished, but in the opinion of the writer it will never be used for commercial purposes, simply because it can not, even if developed to the highest state of perfection, compete with transit on the surface of the earth, either in speed or cost of transportation. It may be used in warfare, but more than likely it will be confined to pleasure purposes.


The highest value can obviously be given to present research by directing it chiefly to those departments which are undergoing most rapid changes and therefore most urgently demand immediate study. The subject is thus regarded by Prof. A. C. Haddon, who, trying to put himself at the point of view of our successors a hundred or a thousand years hence, asks, in Nature, what they would wish we had done. Studies in the structure, development, and physiology of animals, polar research and deep-sea research, will not suffer materially if the pursuit of them is delayed; but "our first and immediate duty is to earn for science vanishing knowledge; this should be the watchword of the present day." In this category are the study of native fauna and flora before they are exterminated or crowded out or mixed with introduced species, and the study of native man before he is contaminated by contact with civilization. The opportunity for these studies is diminishing, and once lost can never be recovered.