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are for some reason or other continually such substances are constantly sending projecting at enormously great velocities forth from their surfaces streams of two kinds of particles, one will not be particles propelled with almost incredible surprised to find that these substances velocity; for if these particles are promaintain a temperature above that of jected from all of the molecules of the the surrounding atmosphere. This has active substances, it would, as a natural been proved experimentally only for result, be expected that the temperature radium, which has been found by MM. of the substance would rise under the Curie and Laborde to remain perma- unceasing internal bombardment. nently at a temperature between one and But from what source
comes this two degrees centigrade above that of its
energy represented in the projected surroundings, and to give out for each
particles, and of which this heat and gram.of its weight enough heat per hour light are the ultimate manifestation?
Radio-activity a Manifestation of Subatomic
The answer to this last question has not yet been fully given. This much, however, can be said—thanks to the magnificent work of Rutherford of McGill University of Sir William Crookes in England, of the Curies and of Becquerel in Paris, and of one or two German physicists—that a fairly satisfactory answer is at least in sight.
Whatever be the cause of the ceaseless emission of particles by radio-active
substances, it is certain that it does not FIG. 4. RADIOGRAPH OF KEYS.
lie in any ordinary chemical reactions
such as those with which we have From a plate taken by means of radium, by W.P. Near, B. A., assistant to Prof. J. C. McLennan, in
heretofore been familiar; for Madame the Physical Laboratory of the University of Tor Curie proved, when she originally disonto. In the taking of the radiograph of which the above is a reproduction, the keys were placed covered the activity of thorium, that the upon a sensitized photographic plate protected by cardboard. Time of exposure, 40 minutes, Strength
radial energy of all the active substances or intensity of radium, 1,500,000. The reader will note the resemblance of the result to that obtain
is proportional simply to the amount of ed by means of X-rays.
the active element (uranium, thorium, or
radium) which is present, and has nothto raise a hundred grams of water ing whatever to do with the nature of through one degree. Since radium radi the chemical compound in which that ates over a million times more actively element is found. Another most striking than either of the other substances, it is property of radio-activity is that it is not probable that any one will ever be independent of all changes in physical able to show directly by experiment that as well as chemical conditions. A radiouranium and thorium also maintain active substance can be subjected to both temperatures above that of their sur the lowest and the highest temperatures roundings. Nevertheless, in all proba- obtainable without showing any alterability, the same causes that operate to tion whatever in the degree of its maintain the relatively high temperature activity. Radio-activity seems therefore of radium operate also to keep up the to be as unalterable a property of the temperature of both of the other radio substances possessing it as does weight active substances, the only difference itself. It is therefore soinething' entirely being one of degree. Hence it is prob- beyond the range of ordinary molecular able that all radio-active substances are forces. This is certainly strong evidence constantly emitting heat energy to a in favor of the view that radio-action greater or less degree. This is not sur involves a change in the nature of the
The present is the first time in the the atoms of all substances are in history of science that any subatomic extremely rapid rotation.
It appears, store of energy has been tapped by man. therefore, that these rapidly rotating sysThe Mechanism of Radio-activity
tems of heavy atoms such as characterize
radio-active substances, not infrequently It seems probable from the discoveries become unstable and throw off a part of described above, together with other dis their mass. The particles first projected
are probably the Alpha-ray particles, and this process of emitting Alpha particles is probably the first stage of radio activity. The mass left behind is itself unstable and throws off still other particles. The remainder, at least in the cases of thorium and radium, is yet again unstable, and still further particles are projected. We are actually able to follow the disintegration of the atoms through at least four (according to Rutherford, through five) successive stages. How many more stages there may really be, no one can certainly tell; but as soon as
the stable condition is reached and no FIG. 5. RADIOGRAPH OF MEDAL AND COINS. more particles are projected, the product Taken by means of radium, in the Physical Lab
has, of course, ceased to be radio-active, oratory of the University of Toronto. In this case, and its presence can no longer be detected as in that of Fig. 4, the sensitized plate, with the metallic objects upon it, was protected from di by the delicate test of radio-activity. It rect action of the radium rays by means of a cardboard screen. Time of exposure, 50 minutes.
is then only after it has accumulated in Intensity of radium, 1,500,000.
sufficient quantity to be capable of
detection by the ordinary methodscoveries which cannot here be recorded, namely, by spectroscopic or chemical that the atoms of radio-active elements analysis—that it could be expected to be are undergoing a slow but continuous found. process of disintegration into atoms of
The Birth of Helium smaller mass and simpler form. Just why these atoms are disintegrating, and More than two years ago, Rutherford, just how these new types of matter are with this picture of the mechanism of formed, must as yet, of course, be largely radio-activity in mind, made a prediction a matter of speculation; nevertheless which has recently been most remarkably research has gone far enough to enable verified. The history of science scarcely
to form a reasonably plausible affords a more striking instance of the hypothesis as to the mechanism of radio fulfillment of scientific prophecy. Since active change.
the element helium-which, by the way, In presenting this hypothesis, the first was first discovered in the sun by means remarkable fact to be noted is that of a line in the solar spectrum that did uranium, thorium, and radium, the three not agree with the lines of any of our permanently radio-active substances thus known elements, and which was found far discovered, and the only ones which also on the earth only a few years ago can with certainty be classed as elements, by Lord Rayleigh and Professor Ramsay, are the substances whose atoms are the the discoverers of argon—since this elethree heaviest atoms known. Thus the ment helium is found in nature only in atomic weight of uranium is 240, that of connection with radio-active minerals thorium 232, and that of radium 225. (that is, in connection with the salts of There is no other property in which these uranium, thorium, and radium), Rutherthree substances are at all alike. In ford predicted that helium would one their chemical characteristics they are day be found to be one of the ultimate extremely different. Now, according to products of the disintegration of the our modern mechanical theory of heat, radio-active elements.
About a year
later, as we have already seen, Rutherford seemed to lead to the startling conclusion, himself found that the Alpha-ray particle that, in the case of certain elements at had the same mass as the atom of helium. least, the dreams of the old alchemists This pointed still more strongly to the were true, for the radio-active elements confirmation of his original prophecy. all appear to be slowly but spontaneously Last July Professor Ramsay and Mr. transmuting themselves into other eleSoddy actually saw the spectrum of ments. The present indications seem to helium grow out of the emanation from be that this transmutation which is going radium. This pointed to the apparently on in nature is a change from the heavier certain conclusion that helium is being atoms to the lighter ones. Whether any continually formed by the disintegration other heavy atoms than those of uranium, of radio-active substances.
The Life of Radium It appears, therefore, that all of the three heaviest atoms known are slowly disintegrating into simpler atoms, but the process is extremely slow. Despite the incessant projection of particles from radium so strikingly shown by the Crookes spinthariscope, no one has as yet been able to detect with certainty any loss whatever in the weight of radium or any diminution in its activity. Yet, unless the fundamental basis of all physical science is to be overthrown, we may be certain that it does both lose weight and
FIG. 6. SAME AS FIG. 5. in the long run decline in activity. From a knowledge of the amount of heat Except that coins partially covered one another,
In this case the time of exposure was increased energy given off by one gram of radium to 1 hour and 30 minutes. In the original
radiograph, the complete outline of each coin per hour (the quantity of which the
is distinctly traceable in spite of superposition, an Curies and Laborde found to be 100 calo effect apparently not obtainable with X-rays.
This effect is here unfortunately lost in the prories), and from the knowledge of the cess of reproduction. energy represented by each projected particle (this knowledge we possess since
thorium, and radium are thus slowly we know the mass and the velocity of the disintegrating, we cannot say. Alpha particles, the energy in the Beta
other of the known heavy elements, such particles being negligible compared with
as gold, lead, barium, and bismuth, are that in the Alpha)—from these data we undergoing such a change, it is too slow can easily estimate how fast a gram of to be detected even by the delicate test radium is losing weight and how fast
of radio-activity. It is, however, interit is losing activity by the disintegration esting to note that the only change of of its particles. The result of the calcu
this kind thus far discovered to be going lation indicates a period of probably not on in the structure of an atom is in some more than from 30,000 to 100,000
respects similar to the changes that are years when all the radium now in exist
incessantly occurring in the organic ence will have ceased to be radio-active,
world in the structure of molecules. By that is, will have ceased to be radium.
the ordinary processes of decay, the The life of uranium and thorium would
more complex molecules are continually be a million or more times as long, since disintegrating into simpler ones, and in these substances are expending their
so doing are setting free the energy that radio-active energy at about only one
was originally put into them when the millionth the rate of radium.
processes of life first built them up into
their complex forms. So the studies of The Transmutation of the Elements
the last eight years upon radiation seem The discoveries we have attempted to to indicate that in the atomic world, as describe in the preceding have indeed in the molecular, certain heavy, complex
atoms are tending to disintegrate into million times as much energy as that simpler ones.
represented in any known chemical The analogy suggests a profoundly change taking place within a gram interesting question. Is there any proc weight of any compound substance. The ess which does among the atoms what experiments of the last eight years have the life process does among the mole marked most notable advance in cules, which takes the simple forms and science, in that they have proven the builds them up again into more complex existence of this immense store of subones? It would be rash to attempt to atomic energy. It seems highly improbgive any positive answer to such able, however, that this energy can ever query; yet the fact that radium now be utilized on the earth to serve man's exists on the earth, taken in connection economic needs, for thus far we know of with the fact that the life of radium is but three substances that are disengaging short in comparison with the past ages it, and these are changing so slowly that of the earth's existence, certainly seems the rate of evolution of energy is practo point to an affirmative answer.
Radium may possibly prove to be of Subatomic Energies
some practical value in the cure of The energy required to produce such disease, although it is too early yet to changes from the simpler to the heavier assert even this with assurance. But atoms, and the equivalent energy set free even though no practical applications of when the heavier atoms disintegrate into the discoveries of the last eight years simpler ones, are enormously greater should be found, radio-activity will have than the energies involved in any of the served what is surely one of the most ordinary chemical transformations. The useful of all ends-namely, that of disintegration of a gram of uranium or enlarging our knowledge of the ways of thorium or radium sets free at least a nature.
It is estimated that 41,300 locomotives are in use in the United States.
operate on illuminating gas of 650 B. T. U. calorific value.
One of the latest contrivances for facilitating research in tropical waters is
a glass-bottomed boat through which the On the slope of the hill opposite the Philippine exhibit at the St. Louis Ex
investigator may look into the depths of position, the Department of Agriculture
the ocean. The Geographical Society of
Baltimore has adopted these boats as is having a map of the United States made that will cover five acres of ground.
part of its equipment for scientific and The various products of each state will
geographical investigation. This curious be shown on this map.
observation craft is about twenty feet in length, very wide of beam to insure steadiness, and resembles in appearance a large dory. In the center, a square well
is built several feet below the bottom of A new central station being erected the boat and also extends up into it. The at Berlin, Ontario, is to be fitted with walls of this well are painted black to Westinghouse gas engines. The first in reduce reflection and light, and the botstallation will amount to 460 hp., com tom of the well is covered with heavy prising three 13 x 14 three-cylinder 125- plates of perfectly clear glass. Looking hp., and one II X 12 three-cylinder 85 down into this well, with the light shut hp. vertical engines. These engines will out by a rubber cloth thrown over the be used to drive direct-current genera head, the observer can see clearly into tors for furnishing city lighting, and will the quiet depths of the sea.
THINK I am not overstepping the plus stock and for shaping, are now debounds of truth when I say that no signed to do work that twenty-five years other class of machine used in the ago would have been considered impossi
every-day work of the machine ble on the milling machine. Today, howshop has been so perfected in construc ever, we cannot afford to do it in any tion or adapted in application to such a other manner. I have seen pieces of variety of work as has the milling ma work that were being machined to size chine.
and shape on a planer at a cost of sevAs I look back to the days of my ap eral dollars each, transferred to the millprenticeship and compare the milling ma ing machine and the work done more satchines then in use with some of the mod isfactorily at a cost of cents. ern types of universal and manufactur Modern competition has rendered it ing machines, the changes that have taken necessary to reduce the cost of manufacplace appear—and they really are—mar tured articles, while at the same time the velous. Not only have the machines wages of the workmen must be mainbeen improved so as to do work of greater tained. No one factor has been of greater range than before, but it is now realized importance in rendering this possible that a greater variety of work can ad than the modern milling machine. vantageously be done on them than was Not only has the machine been made formerly thought possible.
heavier, the spindle enlarged, the length For a time it was my duty to make the of the bearings increased, and the whole necessary tools, set up the machines redesigned to allow of heavier cuts, themselves, and in quite a large number faster feeds, and the production of more of instances gage the work done. The accurate work at less expense; but the gages were made filing size—that is, the different means of adjustment have been work was milled a trifle large and then arranged in such a manner that, instead filed to fit-because we were not educated of the guesswork formerly necessary, the to a degree where we thought it safe machine can now be adjusted in any dito try to mill the work to a fit, or to finish rection, accurately, to within a fraction of size. Perhaps, indeed, considering the a thousandth of an inch, thus saving valcondition of the machines then in use, it uable time and obviating great expense. would not have been safe to attempt mill These changes have not been the work ing to size. It is now, however, the rule of a minute, nor of a year, but have been to mill to fit; and by milling to finish accomplished step by step, according as size, unless the shape of the piece be it has been found desirable in one shop such as to render such a proceeding out and another to mill work formerly done of the question, we not only eliminate in some other manner. Fixtures and cutthe costly operation of filing, but, as a ters were made that would hold the work rule, work can be machined more accu and cut it to shape, but it was then found rately than it can be filed.
either that the milling machine was too Fixtures to hold the work to be ma light, or the spindle power was not suffichined, and cutters for removing the sur cient, or the feed was not strong enough