by Oliver Sacks
X-rays, it was felt, might have the power to penetrate the most intimate, hidden, secret parts of people’s lives. Schizophrenics felt that their minds could be read or influenced by X-rays; others felt that nothing was safe. ‘You can see other people’s bones with the naked eye,’ thundered one editorial, ‘and also through eight inches of solid wood. On the revolting indecency of this there is no need to dwell.’ Lead-lined underclothes were put on sale to shield people’s private parts from the all-seeing rays. A ditty appeared in the journal Photography, ending,
I hear they’ll gaze
through cloak and gown – and even stays,
those naughty, naughty, Roentgen rays.
My uncle Yitzchak, after being in practice with my father during the months of the great flu epidemic, had been drawn into the practice of radiology soon after the First World War. He had gone on, my father told me, to gain uncanny powers of diagnosis by X-ray, able almost unconsciously to pick up the smallest hints of any pathological process.
In his consulting rooms, which I visited a few times, Uncle Yitzchak showed me something of his apparatus and its uses. The X-ray tube in his machine was no longer visible, as it had been in the early machines, but was housed in a beaked and humped black metal box – it looked rather dangerous and predatory, like the head of a giant bird. Uncle Yitzchak took me into the darkroom to watch him develop an X-ray he had just taken. Dimly, in the red light, translucent almost, beautiful, I saw the outlines of a thighbone, a femur, on the large film. Uncle pointed out to me a tiny hairline fracture, just visible as a grey line.
‘You’ve seen X-ray screening,’ said Uncle Yitzchak, ‘in shoe shops, which show you the bones moving through the flesh.«57» We can also use special contrast media to show us some of the other tissues in the body – it’s marvelous!’
Uncle Yitzchak asked if I would like to watch this. ‘You remember Mr. Spiegelman, the mechanic? Your father suspects that he has a stomach ulcer, and sent him to me to find out. He’s going to have a barium ‘meal.’
‘We use barium sulphate,’ Uncle continued, stirring up the heavy white paste, ‘because barium ions are heavy and almost opaque to X-rays.’ This comment intrigued me and made me wonder why one could not use even heavier ions instead. One could have, perhaps, a lead, or mercury, or thallium ‘meal’ – all of these had exceptionally heavy ions, though, of course, the meals would be lethal. A gold or platinum meal would be fun, but far too expensive. ‘What about a tungsten meal?’ I suggested. ‘Tungsten atoms are heavier than barium, and tungsten is neither toxic nor expensive.’
We entered the examining room, and Uncle introduced me to Mr. Spiegelman – he remembered me from one of our Sunday morning rounds. ‘This is Dr. Sacks’s youngest, Oliver – he wants to be a scientist!’ Uncle positioned Mr. Spiegelman between the X-ray machine and a fluorescent screen and gave him the barium meal to eat. Mr. Spiegelman spooned the paste down, grimacing, and started to swallow it, as we watched on the screen. As the barium passed down the throat and into the esophagus, I could see this filling and writhing, slowly, as it pushed the bolus of barium into the stomach. I could see, more faintly, a ghostlike background, the lungs expanding and contracting with each breath. Most disconcerting of all, I could see a sort of bag, pulsing – that, Uncle said, pointing, was the heart.
I had sometimes wondered what it would be like to have other senses. My mother had told me that bats used ultrasound, that insects saw ultraviolet, that rattlesnakes could sense infrared. But now, watching Mr. Spiegelman’s innards exposed to the X-ray ‘eye,’ I was glad that I did not have X-ray vision myself, and that I was confined, by nature, to a small part of the spectrum.
Like Uncle Dave, Uncle Yitzchak retained a strong interest in the theoretical foundations of his subject and its historical development, and he also had a little ‘museum,’ in this case of old X-ray and cathode-ray tubes, going back to the fragile, three-pronged ones that had been used in the 1890s. The early tubes, Yitzchak said, offered no protection against stray radiation, nor were the dangers of radiation fully realized in the early days. And yet, he added, X-rays had shown their dangers from the start: skin burns were seen within months of their introduction, and Lord Lister himself, the discoverer of antisepsis, issued a warning as early as 1896 – but it was a warning that no one heeded.«58»
It was also apparent from the start that X-rays carried a good deal of energy and would generate heat wherever they were absorbed. Yet, penetrating as they were, X-rays did not have too great a range in air. It was the opposite with wireless waves, radio waves, which, if properly projected, could leap across the Channel with the speed of light. These, too, carried energy. I wondered whether these strange, sometimes dangerous relatives of visible light had perhaps suggested to H.G. Wells the sinister heat ray used by the Martians in The War of the Worlds, published only two years after Roentgen’s discovery. The Martian heat ray, Wells wrote, was ‘the ghost of a beam of light’, ‘an invisible yet intensely heated finger’, ‘an invisible, inevitable sword of heat.’ Projected by a parabolic mirror, it would soften iron, melt glass, make lead run like water, make water explode incontinently into steam. And its passage across the countryside, Wells added, was ‘as swift as the passage of light.’
While X-rays took off, engendering innumerable practical applications and perhaps an equal number of fantasies, they elicited a very different train of thought in the mind of Henri Becquerel. Becquerel was already distinguished in many fields of optical research, and came from a family in which a passionate interest in luminescence had been central for sixty years.«59» He was intrigued when he heard in early 1896 the first news of Roentgen’s X-rays and the fact that they seemed to be emanating not from the cathode itself but from the fluorescent spot where the cathode rays hit the end of the vacuum tube. He wondered whether the invisible X-rays might not be a special form of energy that went along with the visible phosphorescence – and whether indeed all phosphorescence might be accompanied by the emission of X-rays.
Since no substances fluoresced more brilliantly than uranium salts, Becquerel pulled out a specimen of a uranium salt, potassium uranyl sulphate, exposed it to the sun for several hours, and then laid it on a photographic plate wrapped in black paper. He was greatly excited to find that the plate was darkened by the uranium salt, even through the paper, just as with X-rays, and that a ‘radiograph’ of a coin could be easily obtained.
Becquerel wanted to repeat his experiment, but (this was the middle of the Parisian winter and the sky remained overcast) he was unable to expose the uranium salt to the sun, so it lay undisturbed in the drawer for a week, on top of the black-wrapped photographic plate, with a small copper cross in between. But then, for some reason – was it an accident, or a premonition? – he developed the photographic plate anyway. It was darkened as strongly as if the uranium had been exposed to sunlight, indeed more so, and showed a clear silhouette of the copper cross.
Becquerel had discovered a new and much more mysterious power than Roentgen’s rays – the power of a uranic salt to emit a penetrating radiation that could fog a photographic plate, and in a way that had nothing to do with exposure to light or X-rays or, seemingly, any other external source of energy. Becquerel, his son later wrote, was ‘stupefied’ at this finding (’Henri Becquerel fut stupefait’ ) – as Roentgen had been by his X-rays – but then, like Roentgen, he investigated the ‘impossible.’ He found that the rays retained all their potency even if the uranic salt was kept for two months in a drawer; and that they had the power not only to darken photographic plates but also to ionize air, render it conducting, so that electrically charged bodies in their vicinity would lose their charge. This indeed provided a very sensitive way of measuring the intensity of Becquerel’s rays, using an electroscope.
Investigating other substances, he found that this power was possessed not only by uranic salts but uranous ones too, even though these were not phosphorescent or fluorescent. On the other hand, barium sulphide, zin
c sulphide, and certain other fluorescent or phosphorescent substances had no such power. Thus the ‘uranium rays,’ as Becquerel now called them, had nothing to do with fluorescence or phosphorescence as such – and everything to do with the element uranium. They had, like X-rays, a very considerable power of penetrating materials opaque to light, but unlike X-rays, they were apparently emitted spontaneously. What were they? And how could uranium continue to radiate them, with no apparent diminution, for months at a time?
Uncle Abe encouraged me to repeat Becquerel’s discovery in my own lab, giving me a chunk of pitchblende rich in uranium oxide. I took the heavy chunk home, wrapped in lead foil, in my school satchel. The pitchblende had been sectioned cleanly through the middle, to show its structure, and I placed the cut face flat on some film – I had begged a sheet of special X-ray film from Uncle Yitzchak, and I kept this wrapped in its dark paper. I left the pitchblende lying on the covered film for three days, then took it along to him to develop. I was wild with excitement when Uncle Yitzchak developed it in front of me, for now one could see the glares of radioactivity in the mineral – radiation and energy whose existence, without the film, one would never have guessed at.
I was doubly thrilled by this, because photography was becoming a hobby, and I now had my first picture taken by invisible rays! I had read that thorium, too, was radioactive, and, knowing that gas mantles contained this, I detached one of the delicate, thoria-impregnated mantles at home from its base and carefully spread it over another piece of X-ray film. This time I had to wait longer, but after two weeks I got a beautiful ‘autoradiography’ the fine texture of the mantle picked out by the thorium rays.
Though uranium had been known since the 1780s, it had taken more than a century before its radioactivity was discovered. Radioactivity might have been discovered, perhaps, in the eighteenth century, had anyone chanced to place a piece of pitchblende close to a charged Leyden jar or an electroscope. Or it might have been discovered in the middle of the nineteenth century, had a piece of pitchblende, or some other uranium ore or salt, been left in accidental proximity to a photographic plate. (This had in fact happened to one chemist, who, not realizing what had happened, sent the plates back to the manufacturer with an indignant note saying that they were ‘spoilt.’) Yet had radioactivity been discovered earlier, it would have been seen simply as a curiosity, a freak, a lusus naturae, its enormous significance wholly unsuspected. Its discovery would have been premature, in the sense that there would have been no nexus of knowledge, no context, to give it meaning. Indeed, when radioactivity was finally discovered in 1896, there was very little reaction at first, for even then its significance could barely be grasped. So in contrast to Roentgen’s discovery of X-rays, which instantly captured the public’s attention, Becquerel’s discovery of uranium rays was virtually ignored.
CHAPTER TWENTY-ONE
Madame Curie’s Element
My mother worked at many hospitals, including the Marie Curie Hospital in Hampstead, a hospital that specialized in radium treatments and radiotherapy. I was not too sure, as a child, what radium was, but I understood it had healing powers and could be used to treat different conditions. My mother said the hospital possessed a radium ‘bomb.’ I had seen pictures of bombs and read about them in my children’s encyclopedia, and I imagined this radium bomb as a great winged thing that might explode at any moment. Less alarming were the radon ‘seeds’ which were implanted in patients – little gold needles full of a mysterious gas – and once or twice she brought an exhausted one home. I knew my mother admired Marie Curie hugely – she had met her once, and would tell me, even when I was quite small, how the Curies had discovered radium, and how difficult this had been, because they had had to work through tons and tons of heavy mineral ore to get the merest speck of it.
Eve Curie’s biography of her mother – which my own mother gave me when I was ten – was the first portrait of a scientist I ever read, and one that deeply impressed me.«60» It was no dry recital of a life’s achievements, but full of evocative, poignant images – Marie Curie plunging her hands into the sacks of pitchblende residue, still mixed with pine needles from the Joachimsthal mine; inhaling acid fumes as she stood amid vast steaming vats and crucibles, stirring them with an iron rod almost as big as herself; transforming the huge, tarry masses to tall vessels of colorless solutions, more and more radioactive, and steadily concentrating these, in turn, in her drafty shed, with dust and grit continually getting into the solutions and undoing the endless work. (These images were reinforced by the film Madame Curie, which I saw soon after reading the book.)
Even though the rest of the scientific community had ignored the news of Becquerel’s rays, the Curies were galvanized by it: this was a phenomenon without precedent or parallel, the revelation of a new, mysterious source of energy; and nobody, apparently, was paying any attention to it. They wondered at once whether there were any substances besides uranium that emitted similar rays, and started on a systematic search (not confined, as Becquerel’s had been, to fluorescent substances) of everything they could lay their hands on, including samples of almost all the seventy known elements in some form or other. They found only one other substance besides uranium that emitted Becquerel’s rays, another element of very high atomic weight – thorium. Testing a variety of pure uranium and thorium salts, they found the intensity of the radioactivity seemed to be related only to the amount of uranium or thorium present; thus one gram of metallic uranium or thorium was more radioactive than one gram of any of their compounds.
But when they extended their survey to some of the common minerals containing uranium and thorium, they found a curious anomaly, for some of these were actually more active than the element itself. Samples of pitchblende, for instance, might be up to four times as radioactive as pure uranium. Could this mean, they wondered, in an inspired leap, that another, as-yet-unknown element was also present in small amounts, one that was far more radioactive than uranium itself?
In 1897 the Curies launched upon an elaborate chemical analysis of pitchblende, separating the many elements it contained into analytic groups: salts of alkali metals, of alkaline earth elements, of rare-earth elements – groups basically similar to those of the periodic table – to see if the unknown radioactive element had chemical affinities with any of them. Soon it became clear that a good part of the radioactivity could be concentrated by precipitation with bismuth.
They continued rendering their pitchblende residue down, and in July of 1898 they were able to make a bismuth extract four hundred times more radioactive than uranium itself. Knowing that spectroscopy could be thousands of times more sensitive than traditional chemical analysis, they now approached the eminent rare-earth spectroscopist Eugene Demarcay to see if they could get a spectroscopic confirmation of their new element. Disappointingly, no new spectral signature could be obtained at this point; but nonetheless, the Curies wrote,
…we believe the substance we have extracted from pitchblende contains a metal not yet observed, related to bismuth by its analytical properties. If the existence of this new metal is confirmed we propose to call it polonium, from the name of the original country of one of us.
They were convinced, moreover, that there must be still another radioactive element waiting to be discovered, for the bismuth extraction of polonium accounted for only a portion of the pitchblende’s radioactivity.
They were unhurried – no one else, after all, it seemed, was even interested in the phenomenon of radioactivity, apart from their good friend Becquerel – and at this point took off on a leisurely summer holiday. (They were unaware at the time that there was another eager and intense observer of Becquerel’s rays, the brilliant young New Zealander Ernest Rutherford, who had come to work in J.J. Thomson’s lab in Cambridge.) In September the Curies returned to the chase, concentrating on precipitation with barium – this seemed particularly effective in mopping up the remaining radioactivity, presumably because it had close chemical affinities wi
th the second as-yet-unknown element they were now seeking. Things moved swiftly, and within six weeks they had a bismuth-free (and presumably polonium-free) barium chloride solution which was nearly a thousand times as radioactive as uranium. Demarcay’s help was sought once again, and this time, to their joy, he found a spectral line (and later several lines: ‘two beautiful red bands, one line in the blue-green, and two faint lines in the violet’) belonging to no known element. Emboldened by this, the Curies claimed a second new element a few days before the close of 1898. They decided to call it radium, and since there was only a trace of it mixed in with the barium, they felt its radioactivity ‘must therefore be enormous.’
It was easy to claim a new element: there had been more than two hundred such claims in the course of the nineteenth century, most of which turned out to be cases of mistaken identity, either ‘discoveries’ of already known elements or mixtures of elements. Now, in a single year, the Curies had claimed the existence of not one but two new elements, solely on the basis of a heightened radioactivity and its material association with bismuth and barium (and, in the case of radium, a single new spectral line). Yet neither of their new elements had been isolated, even in microscopic amounts.
Pierre Curie was fundamentally a physicist and theorist (though dexterous and ingenious in the lab, often devising new and original apparatus – one such was an electrometer, another a delicate balance based on a new piezo-electric principle – both subsequently used in their radioactivity studies). For him, the incredible phenomenon of radioactivity was enough – it invited a vast new realm of research, a new continent where countless new ideas could be tested.
