Page images
PDF
EPUB
[ocr errors]

at

as

their work is placed upon me as your President, and it is case by the gas when in an incandescent condition. A fifth for my effort to discharge that duty that I ask your inert gaseous element was discovered by Ramsay as generous consideration.

constituent of certain minerals which was proved by its As one might expect, the progress of the knowledge of spectrum to be identical with an element discovered twentynature (for it is to that rather than to the historical, five years ago by Sir Norman Lockyer in the atmosphere moral and mental sciences that English-speaking people of the sun, where it exists in enormous quantities. Lockyer refer when they use the word “ science ") has consisted, had given the name helium to this new solar element, and in the last twenty-five years, in the amplification and fuller Ramsay thus found it locked up in certain rare minerals verification of principles and theories already accepted, and in the crust of the earth. in the discovery of hitherto unknown things which either But by helium we are led back to radium, for it was have fallen into place in the existing scheme of each found only two years ago by Ramsay and Soddy that science or have necessitated new views, some not very helium is actually formed by a gaseous emanation from disturbing to existing general conceptions, others of a more radium. Astounding as the statement seems, yet that is startling and first sight, disconcerting character. one of the many unprecedented facts which recent study Nevertheless I think I am justified in saying that, exciting has brought to light. The alchemist's dream is, if not and of entrancing interest as have been some of the dis- realised, at any rate justified. One element is actually coveries of the past few years, there has been nothing to under our eyes converted into another; the element radium lead us to conclude that we have been on the wrong path decays into a gas which changes into another element, -nothing which is really revolutionary; that is to say, namely helium. nothing which cannot be accepted by an intelligible modifi- Radium, this wonder of wonders, was discovered owing cation of previous conceptions. There is, in fact, continuity to the study of the remarkable phosphorescence, as it is and healthy evolution in the realm of science. Whilst called—the glowing without heat-of glass vacuum-tubes some onlookers have declared to the public that science through which electric currents are made to pass. Crookes, is at an end, its possibilities exhausted, and but little of Lenard, and Röntgen each played an important part in the hopes it raised realised, others have asserted, on the this study, showing that peculiar rays or linear streams contrary, that the new discoveries--such as those relating of at least three distinct kinds are set up in such tubesto the X-rays and to radium-are so inconsistent with rays which are themselves invisible, but have the property previous knowledge as to shake the foundations of science, of making glass or other bodies which they strike glow and to justify a belief in any and every absurdity of an with phosphorescent light. The celebrated Röntgen rays unrestrained fancy. These two reciprocally destructive make ordinary glass give out a bright green light; but they accusations are due to a class of persons who must be pass through it, and cause phosphorescence outside in described as the enemies of science. Whether their atti- various substances, such as barium platino-cyanide, calcium tude is due to ignorance or traditions of self-interest, such tungstate, and many other such salts; they also act on a persons exist; and it is one of the objects of this Associ- photographic plate and discharge an electrified body such ation to combat their assertions and to demonstrate, by an electroscope. But the most remarkable feature the discoveries announced at its meetings and the conse- about them is their power of penetrating substances opaque quent orderly building up of the great fabric of “natural to ordinary light. They will pass through thin metal knowledge, that Science has not come to the end of her plates or black paper or wood, but are stopped by more work—has, indeed, only as yet given mankind a foretaste or less dense material. Hence it has been possible to of what she has in store for it-that her methods and her obtain shadow pictures or skiagraphs by allowing the accomplished results are sound and trustworthy, serving invisible Röntgen rays to pass through a limb or even a with perfect adaptability for the increase of true discovery whole animal, the denser bone stopping the rays, whilst and the expansion and development of those general con- the skin, flesh, and blood let them through. They are ceptions of the processes of nature at which she aims. allowed to fall (still invisible) on to a photographic plate,

New Chemical Elements. There can be no doubt that when a picture like an ordinary permanent photograph is the past quarter of a century will stand out for ever in obtained by their chemical action, or they may be made to human history as that in which new chemical elements, exert their phosphorescence-producing power on a glass not of an ordinary type, but possessed of truly astounding plate covered with a thin coating of a phosphorescent salt properties, were made known with extraordinary rapidity such as barium platino-cyanide, when a temporary picture and sureness of demonstration. Interesting as the others in light and shade is seen. are, it is the discovery of radio-activity and of the element The rays discovered by Röntgen were known as the radium which so far exceeds all others in importance that X-rays, because their exact nature was unknown. Other we may well account it a supreme privilege that it has rays studied in the electrified vacuum-tubes are known as fallen to our lot to live in the days of this discovery. No kathode rays or radiant corpuscles, and others, again, as single discovery ever made by the searchers of nature even the Lenard rays. approaches that of radio-activity in respect of the novelty It occurred to M. Henri Becquerel, as he himself tells of the properties of matter suddenly revealed by it. A new us, to inquire whether other phosphorescent bodies besides conception of the structure of matter is necessitated and the glowing vacuum-tubes of the electrician's laboratory demonstrated by it, and yet, so far from being destructive can emit penetrating rays like the X-rays. I say “other and disconcerting, the new conception fits in with, grows phosphorescent bodies," for this power of glowing without out of, and justifies the older schemes which our previous heat-of giving out, so to speak, cold light-is known to knowledge has formulated.

be possessed by many mineral substances. It has brcomp Before saying more of radio-activity, which is apt to familiar to the public in the form of phosphorescent eclipse in interest every other topic of discourse, I must paint,” which contains sulphide of calcium, a substance recall to you the discovery of the five inert gaseous elements which shines in the dark after exposure to sunlight-that by Rayleigh and Ramsay, which belongs to the period on is to say, is phosphorescent. Other sulphides and the which we are looking back. It was found that nitrogen minerals fluor-spar, apatite, some gems, and, in fact, a obtained from the atmosphere invariably differed in weight whole list of substances have, under different conditions of from nitrogen obtained from one of its chemical combin- treatment, this power of phosphorescence or shining in the ations; and thus the conclusion was arrived at by Rayleigh dark without combustion or chemical change. All, howthat a distinct gas is present in the atmosphere, to the ever, require some special treatment, such as exposure 10 extent of 1 per cent., which had hitherto passed for sunlight or heat or pressure, to elicit the phosphorescence, nitrogen. This gas was separated, and to it the name which is of short duration only. Many of the compounds argon (the lazy one) was given, on account of its incapacity of a somewhat uncommon metallic element, called uranium. to combine with any other element. Subsequently this used for giving a fine green colour to glass, are phos. argon was found by Ramsay to be itself impure, and from phorescent substances, and it was, fortunately, one of them it he obtained three other gaseous elements equally inert: which Henri Becquerel chose for experiment. Henri namely neon, krypton, and xenon. These were all dis- Becquerel is professor in the Jardin des Plantes of Paris : tinguished from one another by the spectrum, the sign- his laboratory is a delightful old-fashioned building, which manual of an element given by the light emitted in each

had for me a special interest and sanctity when, a few

ten

state.

years ago, I visited him there, for, a hundred years before, The amount of radium in pitch-blende is one it was the dwelling-house of the great Cuvier. Here Henri millionth per cent. ; rarer than gold in sea-water. The Becquerel's father and grandfather-men renowned through- marvel of this story and of all that follows consists largely out the world for their discoveries in mineralogy, electricity, in the skill and accuracy with which our chemists and and light-had worked, and here he had himself gone physicists have learnt to deal with such infinitesimal quantialmost daily from his earliest childhood. Many an experi- ties, and the gigantic theoretical results which are securely ment bringing new knowledge on the relations of light and posed on this pin-point of substantial matter. electricity had Henri Becquerel carried out in that quiet The Curies at once determined that the minute quantity old-world place before the day on which, about twelve of colourless crystals they had obtained was the chloride Vears ago, he made the experimental inquiry, Does uranium of a new metallic element with the atomic weight 225, to sive off penetrating rays like Röntgen's rays? He wrapped which they gave the name radium. The proof that radium a photographic plate in black paper, and on it placed and is an element is given by its “ sign-manual ”—the spectrum irit lying there for twenty-four hours some uranium salt. which it shows to the observer when in the incandescent He had placed a cross, cut out in thin metallic copper,

It consists of six bright lines and three fainter lines under the uranium powder, so as to give some shape to in the visible part of the spectrum, and of three very the photographic print should one be produced. It was intense lines in the ultra-violet (invisible) part. A very produced. Penetrating rays were given off by the uranium : minute quantity is enough for this observation; the lines ihe black paper was penetrated, and the form of the copper given by radium are caused by no other known element in Toss was printed on a dark ground. The copper was also heaven or earth. They prove its title to be entered on the pinetrated to some extent by the rays from the uranium, so roll-call of elements. that its image was not left actually white. Only one step The atomic weight was determined in the usual way by more remained before Becquerel made his great discovery. | precipitating the chlorine in a solution of radium chloride It was known, as I stated just now, that sulphide of by means of silver. None of the precious element was lost calcium and similar substances become phosphorescent in the process, but the Curies never had enough of it to shen exposrd to sunlight, and lose this phosphorescence venture on any attempt to prepare pure metallic radium. after a lew hours. Becquerel thought at first that perhaps | This is a piece of extravagance no one has yet dared to the uranium acquired its power similarly by exposure to undertake. Altogether the Curies did not have more than light; but very soon, by experimenting with uranium long some four or five grains of chloride of radium to experiment kept in the dark, he found that the emission of penetrating with, and the total amount prepared and now in the hands rays, giving photographic effects, was produced spon- of scientific men in various parts of the world probably does tanpously. The emission of rays by this particular frag- not amount to more than sixty grains at most. When ment of uranium has shown no sign of diminution since Prof. Curie lectured on radium four years ago at the Royal this discovery. The emission of penetrating rays by Institution in London he made use of a small tube an inch uranium was soon found to be independent of its phos- long and of one-eighth inch bore, containing nearly the phorescence. Phosphorescent bodies, as such, do not emit whole of his precious store, wrenched by such determined penetrating rays. Uranium compounds, whether phos-labour and consummate skill from tons of black shapeless phorescent or not, emit, and continue to emit, these pene- pitch-blende. On his return to Paris he was one day demontrating rays, capable of passing through black paper and strating in his lecture room with this precious tube the metallic copper. They do not derive this property from properties of radium when it slipped from his hands, broke, the action of light or any other treatment. The emission and scattered far and wide the most precious and magical of these rays discovered by Becquerel is a new property powder ever dreamed of by alchemist or artist of romance. of matter. It is called radio-activity,” and the rays are Every scrap of dust was immediately and carefully collected, called Becquerel rays.

dissolved, and re-crystallised, and the disaster averted with From this discovery by Becquerel to the detection and a loss of but a minute fraction of the invaluable product. separation of the new element radium is an easy step in Thus, then, we have arrived at the discovery of radiumthought, though one of enormous labour and difficulty in the new element endowed in an intense form with the new practice. Prof. Pierre Curie (whose name I cannot mention property

"radio-activity discovered by Becquerel. The without expressing the grief with which we all heard in wonder of this powder, incessantly and without loss, under April last of the sad accident by which his life was taken) | any and all conditions pouring forth by virtue of its own and his wife, Madame Sklodowski Curie, incited by intrinsic property powerful rays capable of penetrating Becquerel's discovery, examined the ore called pitch-blende opaque bodies and of exciting phosphorescence and acting which is worked in mines in Bohemia and is found also on photographic plates, can perhaps be realised when we in Cornwall. It is the ore from which all commercial reflect that it is as marvellous as though we should dig up uranium is extracted. The Curies found that pitch-blende a stone which without external influence or change, conhas a radio-activity four times more powerful than that tinually poured forth light or heat, manufacturing both in of metallic uranium itself. They at once conceived the itself, and not only continuing to do so without appreciable idra that the radio-activity of the uranium salts examined loss or change, but necessarily having always done so for by Becquerel is due not to the uranium itself, but to countless ages whilst sunk beyond the ken of man in the another element present with it in variable quantities. bowels of the earth. This proved to be in part true. The refuse of the first Wonderful as the story is, so far it is really simple and procrases by which in the manufacturer's works the commonplace compared with what yet remains to be told. uranium is extracted from its ore, pitch-blende, was found I will only barely and abruptly state the fact that radiono contain four times more of the radio-active matter than activity has been discovered in other elements, some very does the pure uranium. By a long series of fusions, solu- rare, such as actinium and polonium ; others more abundant tons, and crystallisations the Curies succeeded in hunt- and already known, such as thorium and uranium, though ing down." as it were, the radio-active element. The first their radio-activity

known until Becquerel's. ***p gave them a powder mixed with barium chloride, and pioneer-discovery. It is a little strange and no doubt having 2000 times the activity of the uranium in which significant that, after all, pure uranium is found to have a Bei querel first proved the existence of the new property- radio-activity of its own and not to have been altogether radio-activity. Then step by step they purified it to a con- usurping the rights of its infinitesimal associate. dition 10.000 times, then to 100,000 times, and finally to The wonders connected with radium really begin when the condition of a crystalline salt having 1,800,000 times the experimental examination of the properties of a few the activity of Becquerel's sample of uranium. The purifi- grains' is made. What I am saying here is tation could go no further, but the extraordinary minute systematic, technical account of radium ; so I shall venture naes of the quantity of the pure radio-active substance to relate some of the story as it impresses me. obtained and the amount of labour and time expended in Leaving aside for a moment what has been done in repreparing it may be judged from the fact that of one gard to the more precise examination of the rays emitted tuin of the pitch-blende ore submitted to the process of by radium, the following astonishing facts have been found purification only the hundredth of a gram—the one-seventh out in regard to it: (1) If a glass tube containing radium of a grain-semained.

is much handled or kept in the waistcoat pocket, it pro

[ocr errors]

66

was

not

not

a seems

duces a destruction of the skin and flesh over

a small from which it was removed forms a new quantity of area-in fact, a sore place. (2) The smallest trace of emanation, having just the amount of radio-activity which radium brought into a room where a charged electroscope has been lost by the old emanation. All is not known is present, causes the discharge of the electroscope. So

about the decay of the emanation, but one thing is absopowerful is this electrical action of radium that a very lutely certain, having first been discovered by Ramsay and sensitive electrometer can detect the presence of a quantity Soddy and subsequently confirmed by independent experiof radium five hundred thousand times more minute than ment by Madame Curie. It is this : After being kept three that which can be detected by the spectroscope (that is to or four days the emanation becomes, in part at least, consay, by the spectroscopic examination of a flame in which verted into helium--the light gas (second only in the list minute traces of radium are present). (3) Radium actually of elements to hydrogen), the gas found twenty-five years realises one of the properties of the hypothetical stone to ago by Lockyer in the sun, and since obtained in some which I compared it, giving out light and heat. For it quantities from rare radio-active minerals by Ramsay! does give out heat which it makes itself incessantly and The proof of the formation of helium from the radium without appreciable loss of substance or energy (" appreci- emanation is, of course, obtained by the spectroscope, and able” is here an important qualifying term). It is also its evidence is beyond assail. Here, then, is the partial faintly self-luminous. Fairly sensitive thermometers show conversion or decay of one element, radium, through an that a few granules of radium salt have always a higher intermediate stage into another. And not only that, but temperature than that of surrounding bodies. Radium has if, as seems probable, the presence of helium indicates the been proved to give out enough heat to melt rather more previous presence of radium, we have the evidence of than its own weight of ice every hour ; enough heat in one enormous quantities of radium in the sun, for we know hour to raise its own weight of water from the freezing- helium is there in vast quantity. Not only that, but inaspoint to the boiling-point. After a year and six weeks a much as helium has been discovered in most hot springs gram of radium has emitted enough heat to raise the and in various radio-active minerals in the earth, it may temperature of a thousand kilograms of water one degree. be legitimately argued that no inconsiderable quantits of And this is always going on. Even a small quantity of radium is present in the earth. Indeed, it now radium diffused through the earth will suffice to keep up probable that there is enough radium in the sun to keep its temperature against all loss by radiation ! If the sun

up its continual output of heat, and enough in the earth consists of a fraction of one per cent. of radium, this will to make good its loss of heat by radiation into space, for account for and make good the heat that is annually lost an almost indefinite period. Other experiments of a similar by it.

kind have rendered it practically certain that radium itsel: This is a tremendous fact, upsetting all the calculations is formed by a somewhat similar transformation of uranium, of physicists as to the duration in past and future of the

so that our ideas as to the permanence and immutability sun's heat and the temperature of the earth's surface. on this globe of the chemical elements are destroyed, and The geologists and the biologists have long contended that must give place to new conceptions. It seems not imprcbsome thousand million years must have passed during able that the final product of the radium emanation after which the earth's surface has presented approximately the the helium is removed is or becomes the metal lead ! same conditions of temperature as at present, in order to It must be obvious from all the foregoing that radiurt allow time for the evolution of living things and the form- is very slowly, but none the less surely, destroying itself. ation of the aqueous deposits of the earth's crust. The There is a definite loss of particles which, in the course of physicists, notably Prof. Tait and Lord Kelvin, refused to time, must lead to the destruction of the radium, and it allow more than ten million years (which they subsequently would seem that the large new credit on the bank of time increased to a hundred million)-basing this estimate on given to biologists in consequence of its discovery has a the rate of cooling of a sphere of the size and composition definite, if remote, limit. With the quantities of radium of the earth. They have assumed that its material is self- at present available for experiment, the amount of loss of cooling. But, as Huxley pointed out, mathematics will particles is so small, and the rate so slow, that it came not give a true result when applied to erroneous data. It

be weighed by the most delicate balance. Nevertheless it has now, within these last five years, become evident that has been calculated that radium will transform halt ol the earth's material is not self-cooling, but on the contrary itself in about fifteen hundred years, and unless it were self-heating. And away go the restrictions imposed by being produced in some way all the radium now in physicists on geological time. They now are willing to give existence would disappear much too soon to make it ? us not merely a thousand million years, but as many more important geological factor in the maintenance of the as we want.

earth's temperature. As a reply to this depreciatory stateAnd now I have to mention the strangest of all the ment we have the discovery by Rutherford and others that proceedings of radium-a proceeding in which the other radium is continually being formed afresh, and from that radio-active bodies, actinium and thorium, resemble it. particular element in connection with which it was disa This proceeding has been entirely Rutherford's discovery covered-namely, uranium. Hypotheses and experiments in Canada, and his name must be always associated with as to the details of this process are at this moment in fu? it. Radium (he discovered) is continually giving off, apart swing, and results of a momentous kind, involving the from and in addition to the rectilinear darting rays of building-up of an element with high atomic weight bs the Becquerel-an “ emanation ”-a gaseous “ emanation." | interaction of elements with a lower atomic weight, ara This “emanation" is radio-active-that is, gives off thought by some physicists to be not improbable in the Becquerel rays--and deposits “ something upon bodies immediate future. brought near the radium, so that they become radio-active, The delicate electric test for radio-activity has town and remain so for a time after the radium is itself removed. largely applied in the last few years to all sorts and Co This emanation is always being formed by a radium salt, ditions of matter. As a result it appears that the ratt'um and may be most easily collected by dissolving the salt in emanation is always present in our atmosphere: that the water, when it comes away with a rush, as a gas. Sixty air in caves is especially rich in it, as are underground milligrams of bromide of radium vielded to Ramsay and waters. Tin-foil, glass, silver, zinc, lead, copper, platinum Soddy 0.124 (or about one-eighth) of a cubic millimetre of and aluminium are, all of them, slightly radio-active. The this gaseous emanation What is it? It cannot be de- question has been raised whether this widespread radan stroved or altered by heat or by chemical agents; it is a activity is due to the wide dissemination of infinitesimo al heavy gas, having a molecular density of 100, and it can quantities of strong radio-active elements, or whether it is be condensed to a liquid by exposing it to the great cold the natural intrinsic property of all matter to emit Berquere! of liquid air. It gives a peculiar spectrum of its own, and ravs. This is the immediate subject of research. is probably a hitherto unknown inert gas-a new element Over and above the more simply appreciable facts witica similar to argon. But this by no means completes its I have thus narrated, there comes the necessary and the history, even so far as experiments have as yet gone. The cult inquiry. What does it all mean? What are it radium emanation decays, changes its character altogether, Becquerel rays of radio-activity? What must we concier and loses half its radio-activity every four days. Precisely to be the structure and mechanism of the atoms of raciu. at the same rate as it decays the specimen of radium salt and allied elements, which can not only pour forth crasples

9

325

streams of intrinsic energy from their own isolated sub- whole progress in the theory and practical handling of stance, but are perpetually, though in infinitesimal pro- electrical phenomena of late years. The discovery of the portions, changing their elemental nature spontaneously, Hertzian waves and their application to wireless telegraphy so as to give rise to other atoms which we recognise as is a feature of this period, though I may remind some of other elements?

those who have been impressed by these discoveries that I cannot venture as an expositor into this field. It the mere fact of electrical action at a distance is that which belongs to that wonderful group of men, the modern hundreds of years ago gave to electricity its name. The physicists, who with an almost weird power of visual power which we have gained of making an instrument imagination combine the great instrument of exact state- oscillate in accordance with a predetermined code of signalmesit and mental manipulation called mathematics, andling, although detached and a thousand miles distant, does possess an ingenuity and delicacy in appropriate experiment not really lend any new support to the notion that the oldwhich must fill all who even partially follow their trium- time beliefs of thought-transference and second sight are phant handling of nature with reverence and admiration. more than illusions based on incomplete observation and Such men now or recently among us are Kelvin, Clerk imperfect reasoning. For the important factors in such Maswell, Crookes, Rayleigh, and J. J. Thomson.

human intercourse-namely, a signalling-instrument and a Becquerel showed early in his study of the rays emitted code of signalshave not been discovered, as yet, in the by radium that some of them could be bent out of their structure of the human body, and have to be consciously straight path by making them pass between the poles of devised and manufactured by man in the only examples of a powerful electromagnet. In this way have finally been thought-transference over long distances at present disdistinguished three classes of rays given off by radium : covered or laid bare to experiment and observation. (1) the alpha rays, which are only slightly bent, and have High and Low Temperatures.-The past quarter of a little penetrative power ; (2) the beta rays, easily bent in a century has witnessed a great development and application direction opposite to that in which the alpha rays bend, of the methods of producing both very low and very high and of considerable penetrative power; (3) the gamma

temperatures. Sir James Dewar, by improved apparatus, rays, which are absolutely unbendable by the

strongest

has produced liquid hydrogen and a fall of temperature probmagnetic force, and have an extraordinary penetrative ably reaching to the absolute zero. A number of applicapower, producing a photographic effect through a foot

tions of extremely low temperatures to research in various thickness of solid iron.

directions has been rendered possible by the facility with The alpha rays are shown to be streams of tiny bodies

which they may now be produced. Similarly high tempositively electrified, such as are given off by gas flames

peratures have been employed in continuation of the earlier and red-hot metals. The particles have about twice the

work of Deville, and others by Moissan, the distinguished mass of a hydrogen atom, and they fly off with a velocity

French chemist. of 20,000 miles a second ; that is, 40,000 times greater than

Progress in Chemistry.--In chemistry generally the that of a rifle bullet. The heat produced by radium is

theoretical tendency guiding a great deal of work has been ascribed to the impact of these particles of the alpha rays.

the completion and verification of the periodic law" of The beta rays are streams of corpuscles similar to those

Mendeléeff ; and, on the other hand, the search by physical given off by the kathode in a vacuum tube. They are

agents such as light and electricity for evidence as to the charged with negative electricity and travel at the velocity arrangement of atoms in the molecules of the most diverse of 100,000 miles a second.

and its They are far more minute than

chemical compounds. The study of “ valency the alpha particles. Their mass is equal to the one

outcome, stereochemistry, have been the special lines in thousandth of a hydrogen atom. They produce the major hundreds, if not thousands, of new chemical bodies have

which chemistry has advanced. As a matter of course part of the photographic and phosphorescent effects of the

been produced in the laboratory of greater or less theoThe gamma rays are apparently the same, or nearly the

retical interest. The discovery of the greatest practical and same, thing as the X-rays of Röntgen. They are probably

industrial importance in this connection is the production not particles at all, but pulses or waves in the ether set

of indigo by synthetical processes, first by laboratory and up during the ejection of the corpuscles which constitute

then by factory methods, so as to compete successfully with the beta rays. They produce the same effects in a much

the natural product. Von Baeyer and Heumann are the smaller degree as do the beta rays, but are

names associated with this remarkable achievement, which

more penetrating

has necessarily dislocated a large industry which derived The kind of conceptions to which these and like dis

its raw material from British India.' coverins have led the modern physicist in regard to the

Astronomy.-A biologist may well refuse to offer any character of that supposed unbreakable body—the chemical

remarks on his own authority in regard to this earliest and atom-the simple and unaffected friend of our youth-are

grandest of all the sciences. I will therefore truly astounding. But I would have you notice that they

say that my friend the Savilian Professor of Astronomy in are not destructive of our previous conceptions, but rather

Oxford has turned my thoughts in the right direction in elaborations and developments of the simpler views, intro

regard to this subject. There is no doubt that there has

been an immense “ revival in astronomy since 1881; it ducing the notion of structure and mechanism, agitated and whirling with tremendous force, into what we formerly

has developed in every direction. The invention of the

“ dry plate," which has made it possible to apply photoconceived of as homogeneous or simply built-up particles, graphy freely in all astronomical work, is the chief cause the earlier conception being not so much a positive assertion of simplicity as a non-committal expectant formula

of its great expansion. Photography was applied to as

tronomical work before 1881, but only with difficulty and awaiting the progress of knowledge and the revelations which are now in our hands.

haltingly. It was the dry-plate which made long exposures As I have already said, the attempt to show in detail

possible, and thus enabled astronomers to obtain regular how the marvellous properties of radium and radio-activity

records of faintly luminous objects such as nebulæ and in general are thus capable of a pictorial or structural

star-spectra. Roughly speaking, the number of stars representation is beyond the limits both of my powers and

11 had at first intended to give in this address a more detailed and the time allowed me; but the fact that such speculations technical statement of the progress of science than I have found possibile fumish a scheme into which the observed phenomena can when actually engaged in its preparation. The limits of time and space what we may take on the authority of the

render any such survey on this occasion imposible, and, moreover, the physirists and chemists of our day.

patience or even the general meeting of the British Association canrot be

considered as unlimited. With a view to the preparation of a more detailed Intimately connected with all the work which has been review, I had asked a number of friends and colleagues to send me notes done in the past twenty-five years in the nature and possible on the progress and tendency in their own par icular branches of science. transformations of atoms is the great series of investi

They responded with the greatest generosity and unselfishness. I must

entirely disclaim for them any responsibility for the brief detached stateBalions and speculations on astral chemistry and the de- inenis made in the address. At the same time I should wish to thank them velopment of the chemical elements which we owe to the here by name for their most kind and timely help. They are: Sir William unremitting labour during this period of Sir Norman

Ramsay, Mr. Soddy; Prof. H. H. Turner, Dr. Marr, Dr. Haddon,
Dr. Smith Woodward, Prof. Sherrington. Prof. Farmer, Prof. Vines, Dr.

D. H. Scott, Prof. Meldola, Dr Macdougal, Prof. Poulton, Mr. C. V. Boys
Wireless Telegraphy. Of great importance has been the Major MacMahon, and Mr. Mackinder.

NO. 1918, vol. 74]

radium rays.

at once

be fitted

Lockyer.

9

seems

to

text-books on the subject (e.g. Rosenbusch's " Microscopical set free from red blood cells, and presumably this body Physiography '') as being cut so that one of its faces is or its derivatives are abnormally abundant in the body exactly parallel to the principal axis (optic axis, axis of fluids. Is there any known organic iron-containing body least elasticity).The difficulty in getting, say, iron-grey capable of being responsible for these quick-change effects of the first order depends on the extreme thinness of the

EDGAR 'TREVITHICK. quartz required at the thin end of the wedge.

Now the interference colour given by plates of equal thickness of the same mineral depends on the direction in

Strength of a Beetle. which they are cut, varying from a maximum when the Last night a small beetle (Aphodius fossor), the length plate is parallel to the optic axis to zero when the plate of which is inch, flew in at my window and alighted is perpendicular to that direction (assuming the mineral on a table next to me. As it buzzed about I put a lid of to be uniaxial). If, then, a wedge be made having one face a tin box over it, but to my surprise the beetle walked parallel to some such direction as, say, any or face of about bearing the lid on its back. I then put the tin box the quartz crystal and its length in the direction of the on the top of the lid, and was absolutely amazed to find trace of the vertical plane of symmetry through that face, that the insect tilted up a corner of the combined box and it will give the same results as the ordinary quartz wedge, lid, and nearly escaped. The weight of the beetle when but, for the same thickness, will give a lower colour, so dead was š grain, alive I suppose it was a little more; that the colours at its thin end may be got very low. On but the box and lid weighed 1758 grains! Assuming that trial a wedge made in this way gave very satisfactory the living insect weighed i grain, it must have tilted up results.

1758 times its own weight! Of course, the strength re The compound wedge described below, which, so far as quired to tilt up a box on edge is nothing like so great as I know, is also new, was found to be still better. Suppose that required actually to lift the weight, but nevertheless a sheet of muscovite be taken, its axes of elasticity deter- the feat

me sufficiently astounding. The mined, and a strip cut of the same size and shape as the dimensions of the box are 34 x 24 x 1} inches. quartz wedge with the axis of greatest elasticity parallel

CHARLES R. KEYSEK. to its greatest length. If the wedge is covered with the The Gables, Hayward's Heath, July 26. mica plate and examined between crossed Nicols, there will, of course, be a black compensation band in some position, and by cleaving the mica thinner this band can be THE INTERNATIONAL CELEBRATION OF made to move towards the thin end of the wedge, and THE JUBILEE OF THE COAL-TAR INfinally to coincide with it. The mica is now cemented to

DUSTRY. the quartz, and a wedge is produced which gives all the colours of the first order. By the use of this compensation DURING, the last centuryno discovery, perhaps, mica plate a very poor wedge may be converted into a first- has led to such far-reaching and important declass instrument, or one broken at its thin end restored to velopments as that of mauve, the first aniline dye, by usefulness.

DANIEL JAMES MAHONY. William Henry Perkin. Not only was the door The Grand Hotel, Melbourne, Victoria, June 25.

thrown open to the never-ending procession of artificial colouring matters, but the raw materials

necessary for their production were also the raw Colour Phenomena in “ Boletus cærulescens.” materials for the synthesis of whole series of entirely One day recently in the woods at Lynton (where the

different substances, which have now assumed most soil is red) I found and gathered two very beautiful toad- important positions in the world's daily requirements. stools, with vermilion stem and bright, sulphur-coloured It cannot be too often repeated that Perkin's dishymenium. In these individuals the striking colour pheno-covery was the result of true scientific devotion to mena peculiar to their family were remarkably in evidence; pure research. The synthetic preparation of quinine in the brilliant sunlight on the bright yellow under-surface was the goal aimed at-a sufficiently ambitious one of the pileus I found my name when traced in the most

for a lad of seventeen, for the problem is yet unsolved. gentle way shine out almost immediately in the most

Perkin did not state, as is perhaps too often done magnificent of blues. Will any of your readers kindly refer me to any recent

nowadays, that “only a black mass was obtained." papers concerning the chemical or physical processes which

His persevering and scientific habit of mind led him underlie this fascinating demonstration? From my own

to investigate the "black mass," with the result that superficial observations it is evident, I think, that light by extraction with alcohol was isolated the violet dye plays an important part. The energy liberated by the very which is so closely associated with his name. gentlest friction appears to be a sufficient initiative.

Great though Perkin's discovery was, yet greater Parts that have been rendered blue, when left at rest, still were the zeal, industry, and genius of the boy oi after a short time return to yellowness, but these same eighteen which enabled him to make the dyestuff on parts are capable under fresh stimulus, so long as the

the large scale and place it on the market successfungus is still alive, of again assuming temporary blue- fully. Only those who have had experience in large

scale preparations can realise what this must have The juice expressed from blue areas is itself bright blue,

meant. New plant, new materials, new conditions : and imparts a bright blue stain to linen. Upon my handkerchief this colour remained so long (at least five hours) all had to be undertaken, and in the introduction of that I thought I had fixed it; but in the morning the dry

iron vessels for the manufacture of his raw material, blue patch of the night before was no longer blue, but aniline, Perkin laid the vast aniline oil industry under yellow.

lasting obligation. On cutting the stem its upper two-thirds was found The start thus given, many entered the field; by endowed with the property of cærulescence; but this was slight variation of Perkin's process Renard not in any degree possessed by its lower third, in which and Franc introduced the splendid crimson dye the cut surfaces remained of a reddish-brown colour. With

magenta ” in France, whilst shortly afterwards the exception of the lower part of the stem and the cuticle, Simpson, Maule, and Nicholson started the manuall the tissues of the fungus exhibited cærulescence.

facture of this colour in London. The happy collabor. I take special interest in these observations on account

ation of A. W. Hofmann, the college professor, with of certain phenomena noticeable in human tissues in the course of a somewhat rarely met with pathological condition

the splendid technical chemist and business man, which has been described under the name chloroma.

E. C. Nicholson, soon not only placed the London Without entering into details, I may remark that along firm in a commanding position, but gave to the world with the colour development which characterises this patho

those researches on rosaniline for which Hofmann logical condition hæmoglobin is probably being extensively | became so famous.

ness.

a

[ocr errors]
« PreviousContinue »