After the inclusion of a number of industrial diseases and injuries in the Workmen's Compensation Acts of 1896 and 1906, the government asked the Royal Society to investigate how and why glare and heat apparently caused glassworkers to develop cataracts during their working lives. The activities between 1908 and 1928 of the Glass Workers' Cataract Committee, which was made up of chemists, physiologists and ophthalmologists, are discussed. Emphasis is placed on the attempts by the octogenarian William Crookes (PRS 1913–15) to formulate a spectacle glass that was opaque to infrared and ultraviolet radiation. While providing relief for industrial workers, the research also laid the foundation for the modern sunglasses industry. Other significant work of the Committee concerned the biochemistry of the eye.
President of the Royal Society
When Sir William and Lady Crookes received the Fellows of the Royal Society and their guests at his first Conversazione in June 1914, his biographer described how
[t]he President stood remarkably erect for his eighty-two years, and wore the Order of Merit on its blue ribbon. He was, as a matter of fact, 5 feet 8 1/2 inches in height, having lost about an inch in the preceding ten years. Lady Crookes [who had been unwell for days] had no airs of the grande dame, but her greeting seemed to convey a genuine welcome. They seemed both to be enjoying the novel dignity of the occasion.1
Crookes (figure 1) was the first and last octogenarian president. He had been elected FRS in 1863 as a result of his discovery of thallium two years before. Apart from an embarrassing public conflict over the Society's rejection of his work on psychic research in the early 1870s, Crookes's relationship with the Royal Society was always close. His major experimental work on the radiometer effect, the spectroscopic investigation of cathode rays, the speculations involving radiant matter that drew upon his examination of the phosphorescent spectra of the rare earth elements, and his influential observations on radioactivity were all published in the Society's Proceedings and Transactions.2 He was a Royal, Davy and Copley medallist (1875, 1888 and 1904), a Vice-President (1895–96, 1907–08 and 1915–16), and the Society's Foreign Secretary (1908–12). Socially, he played a leading role in the amalgamation of the Royal Society's two dining clubs into the new Philosophical Club in 1901. He was an assiduous attendee at Council meetings, and a prominent member of the physics and chemistry publications committee. From 1900 until its reorganization in 1906, Crookes was one of the Society's experimentally active representatives on the government's Boer War Explosives Committee under the leadership of Lord Rayleigh.
After the death of Lord Kelvin at the end of 1907, Crookes took on his mantle as Britain's most distinguished physical scientist. Given this background of international fame and stewardship, Crookes's election as President of the Royal Society in 1912, despite his age, causes little surprise. In fact, however, the election was not straightforward. His chief sponsor, the electrical engineer Silvanus P. Thompson, had to lobby hard and parry suggestions that Crookes was too old for the job, that he had permanently blotted his scientific credentials by never dismissing spiritualism as a falsehood, and that he was an ‘amateur’ who earned his living from commerce.3 That Crookes triumphed over these allegations of unsuitability owed much to his election to the exclusive Order of Merit in 1910, and to his long devoted service to the Society. This included, at the time of his election, membership of a government-sponsored investigation of glass.
Crookes's earlier work on glass
Unlike today's undergraduates, nineteenth-century chemists were well trained in glass-blowing. Crookes learned to blow glass and to make chemical apparatus when he was a student at the Royal College of Chemistry in Oxford Street, London and subsequently when he was A. W. Hofmann's personal assistant there between 1848 and 1853.4 Later, as an independent research worker he passed these valuable skills to his apprentice, Charles Henry Gimingham (1853–90), whose skills rapidly came to outshine those of Crookes. Together they improved the mercury vacuum pump, and, working to Crookes's designs, Gimingham developed the radiometer (1875) and subsequently the delicate miniature apparatus that enabled Crookes to explore ‘repulsion by radiation’ effects, the principal basis of his fame as a chemical physicist.5
As an analytical chemist, Crookes worked with glass apparatus all of his life. It was not, however, until the end of his career that he was forced to take a particular interest in its composition and production. His interest was first sparked by the work of the schoolmaster chemist William Shenstone, who, in conjunction with the metallurgical firm Johnson & Matthey, developed a new formulation of glass blown and worked from melted quartz that was able to withstand very high temperatures. This form of silica glass was therefore extremely well suited for laboratory glassware. Within a few years it had become the preferred form of glass used in laboratories. However, Crookes detected a problem with this glass when working at high temperatures, namely that air leaked through it. He demonstrated this by preparing a very narrow evacuated Crookes tube shaped like a thermometer. When this was placed in an electric furnace at a temperature of 1300 °C for 20 hours he found that the end bulb had devitrified. On opening, there was not the usual sound of the ingress of air on opening a vacuum tube. Suspecting that air had leaked through the devitrified bulb, he proved this by repeating the experiment and opening the tube under mercury, which filled only half of the tube. Examination of the devitrified surface under a microscope showed it had cracked into hexagonal cells. This instantly reminded him of the appearance of a silica evaporating dish he had used to boil down a sample of radium bromide several years before. Like appearances—like causes, he reasoned, concluding that devitrification was caused both by silica glass being exposed to a continuously high temperature and by its being exposed to hot radium salt solutions.6
The electric furnace that Crookes used in this investigation had, at one stage, broken down because of a failure of the heating element. Typically he had carefully investigated this failure and concluded it was due to the fact that although the melting point of platinum was 1753 °C (in fact, that of pure platinum is higher, at 1774 °C), its physical properties altered above about 1500 °C. Close investigations, which Crookes conducted in association with Johnson & Matthey, revealed that above 1500 °C platinum became slightly volatile, thus slowly making a platinum contact thinner until it snapped.7 Although generations of chemists had used platinum crucibles in gravimetric measurements, no one had noticed this volatilization phenomenon before! Did it matter? Crookes carefully weighed one of his platinum crucibles using platinum grain weights that Johnson & Matthey had made for the work he had conducted on the atomic weight of thallium in 1864. After heating it in an electric furnace for two hours at a temperature of 1300 °C, he found a significant sublimation loss of 0.029 grains. He repeated the process some 15 times and plotted the repeated sublimation losses. The same phenomenon occurred with the other transition metals, namely palladium, iridium (which he had recommended as a crucible metal in 1908), rhodium and ruthenium.
These findings threatened to upset all previously recorded analyses, and particularly atomic weight determinations. Crookes therefore repeated the whole cycle of experiments for all of the transition metals at 900 °C, this being the more usual temperature used in electric furnaces for gravimetric analysis. Fortunately, the crucible weight of platinum remained constant, although crucibles made from the other metals did show a gradual deterioration. Analytical chemists were safe as long as they used platinum crucibles and avoided higher temperatures than 900 °C.8
The Royal Society's Cataract Committee
Crookes made his last important contribution to science in an investigation of a glass that could be used in the lenses of spectacles worn to protect the eyes during dangerous industrial processes. Trades unions and lawyers eager to maintain the common law of contract had long campaigned for the financial compensation of workers in dangerous trades and industries who suffered death or forced retirement from work at an early age. The Workman's Compensation Act (1897) ‘gave large groups of injured workers a statutory right of compensation regardless of the fault of their employers, and, indeed, largely irrespective of their own responsibility in bringing about their misfortune’.9 The Act has been seen as the first instalment of the welfare reforms that formed the twentieth century's Welfare State. A further Act passed in 1906 ordered the major industries to make annual returns of the numbers injured and compensated, and authorized the Home Secretary to extend the Act to further occupational groups after expert advice from a departmental committee. Neither Act classed cataract as an industrial disease, despite a growing concern since the beginning of the century concerning the incidence of cataract among those working in the glass-making and iron-smelting industries.
Glassworker's cataract is produced by the opacification of the lens from structural alterations to the cell fibres from which it is constructed. The denaturing of the proteins in the fibres is caused by an interference with the nutritional flow of the aqueous humour around the lens. It is this that produces the opacity. Biochemically, the glutathione content of the lens decreases as the opacity of the lens increases. Evidence gleaned by the Home Office's departmental committee concerning glassworker's cataract was initially inconclusive. In 1907, however, Thomas Legge, the first medical inspector of factories, published firm evidence.10 Accordingly, cataract was added to the compensation schedules in December 1908.11 By the end of World War I some 30 occupations had been included in the schedules of industrial injuries and diseases.
About eight months before glassworker's cataract was added to the schedules of compensable diseases, the government sought the advice of the Royal Society on how glare and heat from glass furnaces and molten glass affected the physical and physiological conditions of the eye sufficiently to cause cataract formation. Doubtless the Home Office's advisory committee believed that if the causes were preventable, it might be possible to avoid payment of compensation to glassworkers. The Royal Society accordingly set up a Glass Workers’ Cataract Committee under the chairmanship of Sir William Abney in June 1908.12 Besides Crookes (who frequently chaired meetings in the absence of Abney), the other members of the Committee included the Oxford physician Clifford Allbutt (who had served on the government's panel on industrial injuries established to monitor the Act), the ophthalmic surgeon Edward Nettleship, the ophthalmologists Marcus Gunn (the first of the Committee to die in office in 1909) and John Herbert Parsons, and the physiologists Hugh Kerr Anderson, John Rose Bradford (then the Society's Foreign Secretary) and Augustus D. Waller. Dr G. J. Burch was added to the Committee a few months later.13 With the exception of Gunn all the members were, or eventually became, Fellows of the Society. At its first meeting two investigative subcommittees were formed. The first (Anderson, Burch, Gunn and Parsons) was primed to visit glass factories to examine working conditions and to collect information on the extent of cataract among employees, while the second (Anderson, Burch, Crookes, Parsons and Waller) agreed to carry out chemical, physical and physiological experiments on the several problems that were to confront the Committee. Crookes and Burch made most of the running in the first group, while Parsons was most prominent in the second. Abney, who had a largely administrative role, was an ex officio member of both subcommittees. It immediately became clear that the Home Office had made no provision for the members’ travelling and experimental expenses, and when Abney demanded a £500 grant the government took the view that the expenses should be drawn from the Royal Society's annual £4000 grant, which the Society had already totally committed for 1908–09. After sharp exchanges lasting almost a year, the government finally released £500 to aid the Committee's expenses.
The work of Crookes's group
Given the uncomfortably hot conditions in which glassblowers worked, it was a reasonable assumption that any damage done to their eyes was due to infrared radiation. Burch began work immediately on an empirical study of whether protective glass screens would allow workers to see what they were doing while shielding them from damaging glare. Aided by his demonstrator, T. G. Malpas, at the Physiological Laboratory in Oxford, Burch used Nernst filaments as sources because of their high temperatures and steadiness of light. These lamps were bought with the Committee's grant. The two men gathered much useful data on the percentages of light transmitted through various tinted glasses and also showed that transmission of radiation was dampened when thin coats of metallic film were applied to glasses. Unfortunately, such films caused blurring of images, which would have been dangerous for any bottle blower in factory conditions. The application of gauze screens in front of blue glass screens was also effective, but again raised doubts as to whether optical definition would be compromised.14
Meanwhile, Crookes undertook long-term research into how the addition of metal oxides to glass recipes might produce a glass that would reflect infrared light produced in the glare of white-hot furnaces. Made into safety spectacles, such a glass would prevent, or at least reduce, damage to the eyes of workmen fashioning molten glass. Crookes's investigations were partly made at his home laboratory in Notting Hill with his assistant James Gardiner (who had replaced Gimingham in 1881), and partly at the 230-year-old Whitefriars glassworks of Harry Powell, an Oxford-educated chemist. The firm of James Powell & Sons had been distinguished for its manufacture of coloured (stained) glasses since 1851.15 Crookes also took photographs of the spectra of molten glass while visiting the Nuttall bottle works in St Helens, the owner being particularly keen to save his workforce's eyesight. Although Nuttall had the opening in a glass furnace bricked up, leaving a small hole for the spectroscope, the fiercely hot conditions cannot have been pleasant for an 80-year-old man, and it was Gardiner who undertook much of the on-site measurements. Several of the exposures taken lasted three-quarters of an hour.
Crookes rapidly determined that any worker exposed to the brilliant light from the furnace for three hours would receive a massive dose of infrared radiation, and he recalled how the Palm House at Kew Gardens used pale-green glass opaque to the infrared. He believed that ‘spectacles or screens made of this glass might be of use in glassworks if the workmen would use them’.16 By 1909, however, Crookes became aware of French and German research showing that pathological changes to the eye lens were probably caused by ultraviolet radiation and that French glassmakers had succeeded in developing a coloured glass that dampened its transmission. This amber-coloured ‘Euphos glass’ rapidly entered the catalogues of spectacle manufacturers all over the world, the prescriptions being especially recommended for the goggles of sportsmen and drivers of automobiles. Crookes and Gardiner believed that this kind of tinted glass could be bettered if the absorption spectra of different types of glass were accurately determined.
It was not until the summer of 1911 that Crookes was able to report to the Committee on successful formulations after appraising and comparing about 160 different combinations of metallic glass with white clear glass. In theory, he told the Committee, ‘it should be possible to make a glass which would be opaque to the infrared and the ultraviolet, and my endeavours have been directed for some time towards that end, but hitherto I have not been successful’.17 Clearly, a compromise formulation would be necessary. Interestingly, he first tested the suitability of each metal ion by cutting a specimen of a pure metal into a thin plate 2 mm thick and using it as a radiometer vane to determine the relative order in which heat was cut off. Each metal was then tested spectroscopically to identify the limits of its ultraviolet spectrum, as well as its opacity (percentage of light rays transmitted) and colour in a tintometer. These tests had shown him that it was worth experimenting with glass mixtures containing small quantities of the oxides or salts of cerium, chromium, cobalt, copper, iron, lead, manganese, neodymium, nickel, praesodymium and uranium. Meanwhile, the government was badgering the Committee for results, but Crookes needed another two years' intermittent research and the inspiration of Faraday's glass researches before he was ready to go public.18
An interim report on the Committee's work and conclusions was sent to the Home Office in April 1911, after which the government gave a further £100 towards a fuller investigation of the effects of light absorption on vision because it might have a bearing on the work of another government investigation of the lighting in factories and workshops, in which Parsons was centrally involved. The Committee decided, however, that it would need at least £200 to accomplish this. To pump the government for the additional £100 the Committee urged Crookes to write up his results quickly as proof that the research was offering value for money. Crookes's private report was subsequently formally presented to the Royal Society a month into his presidency in November 1913. The Home Office was clearly impressed and presented the Committee with the additional £200 in January 1914. The paper announced a formulation that cut off 90% of heat radiation, was opaque to ultraviolet light, and was relatively free of colour so that objects remained clear to the eye. Crookes noted that, besides glassworkers, there would be an advantage in preparing such coloured or tinted glasses to prevent glare for people exposed to sunlight reflected off cliffs, snow, or even electric light.
During the brilliant weather of the late summer  I wore some of these spectacles with great comfort; they took off the whole glare of the sun on chalk cliffs, and did not appreciably alter the natural colours of objects. Lady Crookes, whose eyes are more sensitive to glare or strong light than are my own, wore them for several hours in the sun with great comfort.19
Crookes was not the first to prepare tinted lenses for leisure use, but here was the origin of scientifically formulated Crookes lenses or modern sunglasses.20
Crookes tested more than 300 tinted glasses for this swansong research project, each formulation receiving a serial number that entered the glass literature. The formulations he produced included ‘specimens suitable for spectacles adapted to all requirements—from Eyes of Youth to Eyes of Age’ (type 302). To cut off heat radiation he recommended Crookes Glass 246 (a sage-green glass containing ferrous oxalate with red tartar and wood charcoal) that eliminated 98% of the incident heat; for cutting out ultraviolet light the best glass was Crookes 158, containing cerium borate and ferric and chromic oxides; and for sunglasses the best choice was a pale blue Crookes 249 (Chance's Crookes Glass A1) containing cerium nitrate with a little ferric oxide and cobalt sulphate. All these glass formulations had been prepared with the cooperation of Chance Brothers at Birmingham, who exhibited samples at a Royal Society Conversazione in 1914,21 and by Powell's Whitefriars glassworks in London.22 The five-year research project also proved of considerable significance with the outbreak of war in August 1914.
After the publication of the Royal Society paper and publicity in the opticians' trade press, Crookes was inundated with letters from ordinary people suffering from troubles with their eyesight, as well as financial offers from glass manufacturers who wanted to use his name to promote the sale of some of his glass recipes. Crookes and Gardiner accepted an offer from the Wigmore Street opticians owned by Sir William Wingate and his son Frank Nelson Wingate for the marketing of tinted sunglasses as soon as it was technically possible to produce the glass formula on a large scale. In the event, the war prevented any commercial production and there were unexpected technical difficulties. Large-scale production took place only in the 1920s, when sunglasses were frequently referred to as ‘Crookes Lenses’. Ironically, the original basis of Crookes's investigation, the prevention of cataract, largely dropped out of sight. However, the development of sunglasses in an industrial health context probably explains why Crookes did not explore the possibility of using polarizing lenses. In fact it was not until 1929 that the American Edward H. Land began developing a cellophane polarizing filter that led to the marketing of Polaroid sunglasses from about 1936.
The British optical trade continued to refer to anti-glare recipes as ‘Crookes glass 246’, and so on, for many years afterwards.23 Chance Brothers supplied Crookes glass formulations to the American Optical Company at Southbridge, Massachusetts, until 1922, when prohibitive tariffs on imports forced the American company to cancel its orders and develop its own ultraviolet-absorbing glass. This loss of trade actually gave a fillip to Chance's British trade, and an advertising campaign, in which a drawing of a bearded Crookes figured prominently, promoted the sale of spectacles containing Crookes lenses. A happy accident at Chance's works in Birmingham in the 1920s led to a batch of ‘Chance's Crookes glass A1’ (Crookes 249) becoming contaminated with blue cullet. Because of the rather pleasant blue tint, Chance decided to market it rather than scrap it. As a result, glass type Crookes A2, patented in 1926, became very fashionable.24 Ironically, it was only much later that it was understood that what caused visual discomfort was not so much ultraviolet light as the intensity of sunlight. A decade after their father's death, his executors, Bernard and Lewis Crookes, tried to establish whether they were owed royalties on sales by Wingate's and Chance Brothers, but the outcome is not known.25
The work of Parsons's group
The other subcommittee of ophthalmologists and physiologists was dominated by Parsons, who took the lead in its research. After visiting various glass factories in the north of England and examining case histories of cataract among glassworkers recorded by local general practitioners at home and abroad, the group concluded that bottle makers were especially prone to developing cataracts in the centre of the posterior cortex. In contrast, when Parsons visited the Salem Glass Works in New Jersey in 1910, where machinery was used for blowing and moulding bottles, he found little incidence of cataract among its workers. The Committee concluded that cataract was rare among makers of pressed glassware and of bottles made from flint glass. As a result of these findings, Parsons's group began detailed investigations of the mechanisms by which radiant energy affected the eye, using the remainder of the original grant in the process. Parsons and his University College London colleague E. E. Henderson duly experimented with the effects of ultraviolet radiation on the cornea, lens and vitreous humour of rabbits' and frogs' eyes. Because the results were not clear cut, they asked the Cataract Committee to commission E. K. Martin at University College Hospital to make much more detailed and controlled investigations. Martin showed that opacity was definitely developed when the animals' eyes were exposed to radiation from a mercury-vapour lamp. Controls gave consistently negative results. The general conclusion from these tests was that radiation somehow damaged the ciliary body, which in turn caused malnutrition of the lens and the creation of opacity.26
The Cataract Committee was obliged to stop all of its work between 1915 and 1921 because of the national emergency. Nevertheless, similar experiments were conducted on behalf of the Committee by the young Archibald V. Hill working at Cambridge under the supervision of the physiologist Hamilton Hartridge during the first few months of the war and using the £200 awarded by the government in 1914 for instruments. Hartridge and Hill showed how infrared radiation between 1100 and 700 μμ (i.e. between 11×10−4 and 7×10−4 cm) passed unchecked through most animal eye lenses until it reached the retina. They investigated the eye's lymphatic system and demonstrated that infrared radiation slowly affected the proteins making up the lens material by interfering with its nutrition.27
The Committee's demise
Shortly after the cessation of hostilities, in December 1919 the Home Office asked whether the Committee intended to resume its investigations. Parsons, who was extremely keen to continue, quickly concocted a report on Hartridge's and Hill's earlier work and assured the government that new investigations were planned. In fact it was not until 1921 that the work of the Committee was restarted under the direction of Bradford (who had replaced Abney after his death in 1920). By then five others of the original Committee (Abney, Crookes, Gunn, Nettleship and Waller) had died. Significantly, they had been replaced by physiologists and biochemists (namely Henry Dale, William Hardy, A. V. Hill and L. E. Hill) rather than chemists and ophthalmologists.28 Information received from the Wolverhampton Eye Infirmary confirmed that cataracts also formed in the eyes of puddlers and tin-plate millmen, and the Committee agreed to investigate this further with the help of Legge, who was by then the Chief Medical Inspector of Factories. As a result, the Committee recommended that foundry and mill men who developed cataracts should be eligible for compensation.29 Additionally, in continuation of the informative investigations begun by Hartridge and Hill, the Committee commissioned Mrs C. A. Harris at Moorfields Hospital to investigate the ‘colloidal chemistry’ (that is, the biochemistry) of the lens.30
In the event, Harris's report proved profoundly unsatisfactory and the Committee did not recommend its publication or that it should be sent to the Home Office. Instead, probably on the advice of Gowland Hopkins, the investigation was passed to Dorothy Rose Adams, who had graduated from Girton College with first-class honours in physiology in 1923. A removal man's daughter who was keen to take up medicine as a career, Adams obtained a postgraduate award from the Gilchrist Educational Trust in 1924 to support her research.31 Using fresh ox and sheep lenses she brilliantly demonstrated that clouding of the lens was due to an autoxidation process comparable to one previously established by Hopkins in muscle. This decreased the amount of glutathione in the lens, a presumptive factor in the creation of cataract. Adams (Dr Dorothy Campbell, as she became from 1931) went on to become a distinguished ophthalmic surgeon.
The Committee was wound up in the summer of 1928, when its pioneering work (together with a cash balance of £102 4s. 8d.) was transferred to the new Medical Research Council, whose Vision Committee (which included Adams) built on the Royal Society's work to produce a better understanding of the causes of glaucoma, as well as cataract.32 Ironically, the Cataract Committee's final report in 1928 revealed that all attempts to persuade workers to use Crookes glass spectacles had failed ‘owing to the innate conservatism of the British workman’.33 Fortunately, by then the introduction of machinery for bottle blowing had considerably diminished British workers' exposure to harmful radiations. As to the causes of industrial cataract, the Committee concluded it was due to the indirect effect of ultraviolet and infrared radiation on the nutritional biochemistry of the lens and ciliary bodies.
The Cataract Committee's research into the causes of glassworker's cataract and of possible methods of prevention fell into two phases. Prewar work activity was dominated by the indomitable Sir William Crookes, whose knowledge of rare-earth chemistry and spectroscopic skills were used to identify glass formulations that cut down glare. Although many different kinds of tinted glass had been made empirically over the centuries (notably for stained glass windows), Crookes was the first chemist to study glass from a spectroscopic point of view. The work he published in 1914 when President of the Royal Society led to the creation of the sunglasses industry after his death in 1919. On the other hand, glassworkers themselves seem to have rejected his tinted glasses. Fortunately for them, however, the mechanization of bottle making after the end of the war brought about its own reduction in the incidence of cataract among glassworkers.
In a second phase of the Committee's work, led mainly by Sir John Parsons, the biochemistry of the eye was investigated. The task was given to young research workers such as A. V. Hill and Dorothy Adams, and helped to establish their careers. Another beneficiary of the Committee's work was Crookes's assistant James Gardiner, who, after Crookes's death in 1919, succeeded James Powell as Managing Director of the Whitefriars glassworks. Although sponsored by the government to the tune of £500, most of Crookes's research was paid for from his own pocket. Other members of the Committee, such as Parsons, farmed research out to their hospital assistants or to the growing postwar band of postgraduate students such as Adams. Finally, in the postwar era the surviving members of the Committee found that the subject of their interest overlapped with some of the activities of the Medical Research Council that the government had founded as part of the war effort. It therefore seemed logical for the Royal Society to hand over further research to this government-sponsored body in 1928.34
I am grateful to the Librarian of the Royal Society for permission to quote from the Cataract Committee's minutes. Peter W. J. Bartrip (University of Northampton) kindly suggested how to determine when cataract became a compensatory disease. Kate Perry, Girton College archivist, gave invaluable assistance in the identification of Dorothy Adams.
- © 2007 The Royal Society