ISAAC   ROBERTS (1829-1904)

Introduction

Isaac Roberts was born in 1829 at Y Groes, a village several miles to the west of the town of Denbigh in northeast Wales. He spent some of his childhood there, before settling with his family in Liverpool in northwest England. He worked in Liverpool as a builder, eventually making a fortune in the construction industry. Having reached financial security, he was able to pursue his leisure interests, in particular astronomy.

Isaac Roberts took up astrophotography, which had already achieved some success in fields such as the accurate measurement of the positions of celestial objects. However, the potential of photography to record faint images invisible to the eye was largely undeveloped. Roberts pioneered such long-exposure photography, initially with large lenses on accurately tracking mountings. He later turned to photography through telescopes, purchasing a large telescope with a 20-inch mirror built to his own exacting specifications and carefully designed by him to track astronomical objects across the sky with unprecedented steadiness.

Roberts succeeded in photographing many star clusters and nebulae. He revealed unknown details in these nebulae (which included both interstellar gas clouds and what we known today to be galaxies). For example, he was the first person to identify the spiral shape of the Great Andromeda Nebula, showing it to be the same type of object as the spiral nebulae (what we know today to be spiral galaxies, with the Andromeda Nebula the nearest to our own Galaxy). He found that the Pleiades star cluster contained extensive nebulosity between the stars: the extent of this nebulosity was unexpected. Roberts found the Great Orion Nebula to be much larger than previously thought and found a complex structure inside the nebula. He published many of these photographs in the book A Selection of Photographs of Stars, Star-clusters and Nebulae, published in two volumes (the first in 1893, and Volume II in 1899).

The importance of Isaac Roberts's work was recognised internationally. He was honoured by being being elected a Fellow of the Royal Society, the highly prestigious national academy of sciences of Britain. He was awarded an honorary doctorate in Dublin (though curiously not by the University of Wales). He received the gold medal of the Royal Astronomical Society in London. He met the American astronomer Dorothea Klumpke on an eclipse expedition and they later married. He died in 1904. A crater on the Moon has been named Roberts to honour him (actually it is named after both Isaac Roberts and Alexander W. Roberts, a South African astronomer, 1857-1938): it is situated on the Far Side of the Moon, close to the lunar North Pole.

Although he lived most of his life outside Wales, and carried out his astronomical work in England (in Birkenhead, Liverpool and Sussex), he continued to have strong links with his native country. He therefore commands a very prominent position in our survey of Welsh astronomers.

Left: The 20-inch and 7-inch telescopes in Isaac Roberts's observatory. The 20-inch reflector was used for photography. This picture was taken from the introduction to the book A Selection of Photographs of Stars, Star-clusters and Nebulae, The Universal Press, London, 1893.

Left: Isaac Roberts's home and observatory, Starfield, at Crowborough in Sussex. Taken from A Selection of Photographs of Stars, Star-clusters and Nebulae (1893).

Left: Isaac Roberts's photograph of the Great Andromeda Nebula, M31, showing the spiral structure. Taken from A Selection of Photographs of Stars, Star-clusters and Nebulae, Volume II, The Universal Press, London, 1899.

Left: His photograph of the Triangulum spiral nebula, M33, now known to be a Local Group galaxy. From A Selection of Photographs of Stars, Star-clusters and Nebulae, Volume II (1899).

Left: His photograph of the Veil Nebula in Cygnus. From A Selection of Photographs of Stars, Star-clusters and Nebulae, Volume II (1899).

Account in Seryddiaeth a Seryddwyr

It reads as follows (with a translation into English to follow):

ISAAC ROBERTS, D.SC., F.R.S., F.R.A.S. (1829-1904). Genedigol o'r Groes, ddwy filltir o Dinbych. Credwn yr eddyf pawb mai hwn yw yr un o'r seryddwyr mwyaf, os nad y mwyaf oll, a fagodd Cymru erioed. Heblaw y gydnabyddiaeth a wnaed uchod i'r Parch O. J. Owen, yr wyf yn ddyledus hefyd i Mr. Isaac Davies, 41, The Woodlands, Birkenhead, am rai manylion am Dr. Isaac Roberts. Ceir hanes da am dano yn y Geninen am 1904 gan y diweddar Eleazar Roberts, ac eto gan yr un awdur yn yr Ywelydd Misol, am Awst, 1905. Mae'n debyg fod ei rieni wedi ymfudo i'r America pan oedd yn blentyn, ond wedi dychwelyd yn lled fuan i Lerpwl. Prentisiwyd ef gyda Mri. Johnson, contractors, a chadodd yn raddol yn ei fusnes, ac enillodd lawer o gyfoeth. Gwrteithiai ei feddwl ar yr un pryd, drwy Seryddiaeth yn bennaf. "Arsyllai" yn Rock Park and Maghull, ac yn ddiweddarach adeiladodd Arsyllfa, yr hon a gostiodd filoedd o bunnau, yn Crowborough, Sussex. Tynnu gwawl-luniau (photos) o'r sêr oedd ei hoff waith. Cyhoeddodd ddwy gyfrol werthfawr- Photos of Stars, Star-clusters and Nebulae [A Selection of Photographs of Stars, Star-clusters and Nebulae, The Universal Press, London, 1893; Volume II, 1899]. Mae ei lafur wedi helaethu ein gwybodaeth seryddol yn aruthrol. Yn ei flynyddoedd olaf cafodd lawer o gynhorthwy gan ei ail wraig, Dorothea Klumpke Roberts, sydd ei hun yn y rheng flaenaf ymhlith seryddwyr, ac yn awr [1923] yn byw yn San Francisco. Fel prawf o'i serch at ei wlad, yr hon a garai yn angherddol- yr oedd yn Gymro i flaenau ei fysedd- gadawodd yn ei ewyllys swm tywysogaidd i Golegau Caerdydd, Bangor, a Lerpwl. Bu farw yn dra sydyn yn 1904 yn Crowborough yn 75 mlwydd oed. Ar ol cremation bu ei ludw yn gorwedd yno am tua pum mlynedd, pryd y codwyd ac yr ail-gladdwyd ef yng nghladdfa Flaybrick Hill, Birkenhead. Mae ei fedd-argraff yn nodedig:-

"In memory of Isaac Roberts, Fellow of the Royal Society, one of England's pioneers in the domain of Celestial Photography. Born at Groes, near Denbigh, January 27, 1829, died at Starfield, Crowboro, Sussex, July 17, 1904, who spent his whole life in the search after Truth, and the endeavour to aid the happiness of others. Heaven is within us. This stone is erected in loving devotion by his widow
Dorethea Roberts née Klumpke."

Ar dalcen arall y garreg ceir :-

"Heaven is within us, and we have the power to dwell in it all the days of our life in full happiness, or we may decline and make ourselves miserable with `cibau gweigion ffol.' Bydded inni `ddewis y rhan dda.'"

This is Rhys Morris's translation of Silas Evans's account:

ISAAC ROBERTS, D.SC., F.R.S., F.R.A.S. (1829-1904). Born in Y Groes, two miles from Denbigh. I believe he is one of the greatest astronomers, if not the greatest of all, that Wales has ever produced. Besides the acknowledgement made above to the Rev. O. J. Owen, I am indebted also to Mr. Isaac Davies, 41, The Woodlands, Birkenhead, for some details about Dr. Isaac Roberts. A good history is to be had in Y Geninen [The Leek] in 1904 by the late Eleazar Roberts, and again by the same author in the Ywelydd Misol [Monthly Visitor] for August, 1905. It appears that his parents emigrated to America when he was a child, but returned shortly to Liverpool. He was apprenticed to the contractors Messers Johnson, and rose gradually in the business, and secured much wealth. He cultivated his mind at the same time, mainly through astronomy. He "observed" from Rock Park and Maghull, and later built an observatory costing thousands of pounds in Crowborough, Sussex. Taking photographs of the stars was his favourite occupation. He published two valuable volumes- Photos of Stars, Star-clusters and Nebulae [A Selection of Photographs of Stars, Star-clusters and Nebulae, The Universal Press, London, 1893, and Volume II in 1899]. His labours have enlarged astronomical knowledge greatly. In his later years he received a lot of help from his second wife, Dorethea Klumpke Roberts, who is herself in the front ranks of astronomers, and now lives in San Francisco. As proof of his affection for his country which he loves constantly- he is a Welshman to the tips of his fingers- he left a princely sum to the Colleges of Cardiff, Bangor and Liverpool. He died suddenly in 1904 in Crowborough aged 75 years. After cremation his ashes lay there for about five years, after which he was reburied in Flaybrick Hill Cemetery, in Birkenhead. His epitaph is notable:-

"In memory of Isaac Roberts, Fellow of the Royal Society, one of England's pioneers in the domain of Celestial Photography. Born at Groes, near Denbigh, January 27, 1829, died at Starfield, Crowboro, Sussex, July 17, 1904, who spent his whole life in the search after Truth, and the endeavour to aid the happiness of others. Heaven is within us. This stone is erected in loving devotion by his widow
Dorethea Roberts née Klumpke."

On the other side of the stone is:-

"Heaven is within us, and we have the power to dwell in it all the days of our life in full happiness, or we may decline and make ourselves miserable with `cibau gweigion ffol' [foolish empty vessels]. Bydded inni `ddewis y rhan dda.' [May we choose the good part]."

Left: portrait of Isaac Roberts from page 277 of Seryddiaeth a Seryddwyr Below: Isaac Roberts's observatory and home from page 278 of Seryddiaeth a Seryddwyr

Account in the Dictionary of National Biography

ROBERTS, ISAAC (1829-1904), amateur astronomer, son of William Roberts, a farmer of Groes, near Denbigh, North Wales, was born at that place on 27 Jan 1829 ; though in childhood he left Wales with his family for Liverpool, he retained a knowledge of Welsh through life. In 1844 he was apprenticed for seven years to the firm of John Johnson & Son, afterwards Johnson & Robinson, builders and lime burners, of Liverpool. One of the partners, Robinson, died in 1855, and Roberts was made manager. In the next year, the surviving partner died. Roberts, after winding up the concern, began business for himself in 1859 as a builder in Liverpool, and being joined in 1862 by Mr. J. J. Robinson, son of his former master, the firm traded for a quarter of a century under the name of Roberts & Robinson, undertaking many large and important contracts in Liverpool and its neighbourhood. In 1888 Roberts retired with means to allow him to devote himself to scientific research. Whilst still occupied in business, very many branches of science had engaged his attention. Geology was the first subject that he took up seriously. He became a fellow of the Geological Society in 1870, and at the British Associaton meeting of 1878 he read a paper on the filtration of water through triassic sandstone. Between 1882 and 1889 he made an elaborate series of experiments on the movement of underground water as affected by barometric and lunar changes. A paper on a different subject, `the determination of the vertical and lateral pressures of granular substances,' which appeared in the `Proceedings of the Royal Society' for 31 Jan. 1884, embodied the results of elaborate experiemnts made for the purpose of furnishing data to engineers and builders of storehouses.

Meanwhile his attention had been turned to astronomical observation. In 1878 he had a 7-inch refractor by Cooke at his home at Rock Ferry, Birkenhead, which he used for visual observation, but a few years later he applied himself with zeal to the advancing practice of stellar photography. In 1883, a year after his removal to Kennessee, Maghull, near Liverpool, he experimented in photographing stars with rodinary portrait lenses varying in aperture between three-eighths of an inch and five inches. After consideration of the results of these experiments and comparisons with the photograph of the nebula in Orion by Andrew Ainslie Common (q. v. Suppl. II), he ordered from Grubb of Dublin a 20-inch silver-on-glass reflector of 100 inches focal length, the photographs to be taken directly in the focus of the mirror to obviate any loss of light on a second reflection, and the photographic telescope to be mounted on the same declination axis as the 7-inch refractor, one being the counterpoise of the other (Monthly Notices R.A.S. xlvi. 99).

At the meeting of the Royal Astronomical Society of January 1886, Roberts, who was at the time the president of the local astronomical society at Liverpool, reported taking during the past year 200 photographs of stars which might be measured for position, as well as long exposure photographs of the Orion nebula, the Andromeda nebula, and the Pleiades. At the November meeting in the same year he presented a photograph of the Pleiades taken with his 20-inch reflector with exposure of three hours, which showed the stars Alcyone, Maia, Merope, and Electra surrounded by nebulosity extending in streamers and fleecy masses till it seemed almost to fill the spaces between the stars and extend far beyond them. The photograph was accepted as revealing structure about the group never before seen or suspected. A photograph of the great nebula in Andromeda presented at the meeting of December 1888, which suggested that the object is of the spiral type, evoked considrable interest because it was supposed to illustrate the main idea of the nebula hypothesis. Photographs of the great nebula in Orion, presented a few months later, were equally successful. Roberts persistently urged the superiority of the reflector over the refracting telescope, a view that has since received much confirmation. In the early years of his work Roberts designed an instrument, the pantograver, an example of which was made for him by Mr. Hilger, for transferring mechancially the images on a photgraphic negative to a copper plate, to be used for making reproductions (Monthly Notices, Nov. 1888).

Roberts attended by invitation the Conference of Astronomers at Paris in 1887 which initiated the international survey of the heavens by photography, but took no part in the scheme, which was entrusted to professional astronomers at national observatories with instruments of a uniform type. In order to continue his work on the nebulae and star clusters in a clearer atmosphere than that of Liverpool, he finally settled in 1890 at Crowborough Hill, Sussex, in a house appropriately named Starfield. There Mr. W. S. Franks, an astronomer and skilful photographer, became his working assistant, and Roberts confined himself to organisation and supervision. Month by month for several years he exhibited at the Royal Astronomical Society splendid photographs of remarkable objects in the sky taken with his reflector. Two volumes of selections of Roberts's photographs of stars, star clusters, and nebulae, 125 reproductions in all, appeared respectively in 1893 and 1899. In 1896, Roberts, following the example of Professor Barnard in America, added to the equipment of his observatory cameras with portrait lenses of different types, in order to compare their photographic results with those of the reflecting telescope (cf. a discussion on the relative efficiency of the two methods between Roberts and Professor Barnard in R.A.S. Monthly Notices, lvi. 372, lvii. 10, lviii, 392). Between 1896 and 1902 Roberts prepared photographs of fifty-two regions of the sky called nebulous by Sir William Herschel, made with his reflector and with a portrait lens of 5 inches aperture made by Messrs. Cooke of York. No diffuse nebulosity was shown on forty-eight of these plates, a result which was not confirmed by Dr. Max Wolf of Heidelberg, who made special examination of several cases (Monthly Notices, lxiii. 303). Roberts's report of this research was presented in November 1902 (Monthly Notices, lxiii. 26).

Roberts joined the Royal Astronomical Society in 1882. In 1890 he was elected a fellow of the Royal Society, and in 1892 the honorary degree of D.Sc. was conferred on him by Trinity College, Dublin, on the occasion of its tercentenary. In 1895 the Royal Astronomical Society awarded the gold medal to Roberts for his photographs of star clusters and nebulae, the award being announced and the address being deleivers by Captain (now Admiral) Abney, the leading authority on photography, who congratulated him on his `conclusion that a reflector is better for his purpose than a refractor.' Roberts went to Vadso, Norway, on the Norse King, to observe the total solar eclipse of 9 August 1896, but an overcast sky prevented observations.

Roberts, who was a zealous liberal, interested himself in legislation affecting education. He was one of the governors of the University of North Wales [sic.]. He died suddenly at Crowborough on 17 July 1904, and his cremated remains were entombed four years later in a stone in Birkenhead cemetery, Flaybrick Hill, Birkenhead, on 21 July 1908. After providing for his widow and other relatives, he left the residue of his large estate for the foundation of scholarships in the University of Liverpool and the university colleges of Wales, Bangor and Cardiff.

He married (1) in 1875 Ellen Anne, daughter of Anthony Cartmell; and (2) in 1901 Dorothea Klumpke of San Francisco, a member of the staff of the National Observatory, Paris, who had been a fellow voyager on the Norse King in 1896. He had no children.

A photograph is in the British Museum series of portraits at South Kensington.

(Proceedings of the Royal Society, vol. lxxv.; Royal Astronomical Society Monthly Notices, vol. lxvi and as quoted; private information.)

H.P.H. [H. P. Hollis]

Obituary of Isaac Roberts in the Proceedings of the Royal Society

ISAAC ROBERTS. 1829-1904

William Roberts, the father of Isaac, was married in 1825. Like his father before him, William was a farmer, and he lived at Groesback [sic.], near Denbigh. It was here that Isaac was born, January 17, 1829. Though Isaac, while yet in his childhood, ceased to reside in Wales, he retained throughout his life his knowledge of the Welsh language, which he spoke and wrote fluently. It may also be mentioned here that all his life Isaac was passionately attached to music, as well as to science. No doubt the second purchase he made out of his savings was a microscope, but the first was a piano. He had an excellent bass voice, and in after years became an enthusiastic practising member of the Liverpool Philharmonic Choral Society.

On November 12, 1844, Isaac Roberts was bound as an apprentice for seven years to the firm of John Johnson & Son, Builders and Lime Burners in Liverpool - a firm established sixty years previously, with a reputation for good building and prosperity. Mr. Peter Robinson (the father of Isaac Roberts' future partner) had been with that firm for 30 years, and in 1847 was admitted a partner, so that Roberts completed his apprentice with the new firm of Johnson and Robinson. From serving an apprenticeship with freemen, Roberts became a freeman of the City of Liverpool. He was remarkable for his industry and desire for information, and was cited as an example for imitation by the other apprentices. He was by nature a student, and did not care for many of the usual amusements of young people. His evenings were passed at the school of the Mechanics' Institute in Liverpool. For his master, Peter Robinson, Roberts had a deep admiration and tried to imitate his many excellences.

Peter Robinson died in 1855, and Roberts was then made manager of the business of the firm. In 1856 the other partner, John Johnson, died, and Roberts was engaged to wind up the contracts and affairs of the firm. In 1859 Roberts began business in a small way as a hard-working builder in Liverpool, and was very persevering, and in 1862 Mr. J. J. Robinson, son of Peter Robinson, joined him as partner, and the firm became Roberts & Robinson. It is to this partner, the lifelong intimate friend of Roberts, that I am indebted for these particulars.

The first contract of the firm was the construction of the Birkenhead Water Works, situate on Flaybrick Hill, Cheshire, and this was followed by an important undertaking for the Liverpool Gas Company. The contractor for the erection of the Lime Street Station Hotel, at Liverpool, belonging to the London and North-Western Railway Company entrusted the carrying out of the brickwork and mason's work to Messrs. Roberts & Robinson. After a successful career as builders for a quarter of a century, the firm gave up business in 1888, and thus left Isaac Roberts in possession both of the means to provide himself with the best scientific instruments and the leisure to devote himself to their employment.

Some years before the name of Dr. Roberts became known to the scientific world, the present writer remembers hearing the late Earl of Rosse remark on the many instances he knew of men, whom after a successful business career as builders, devoted a well-earned retirement to practical astronomy. It is interesting to note that yet another builder, of whom Lord Rosse had never heard, was destined to develop and carry onwards to an unanticipated importance Lord Rosse's own brilliant discovery of spiral nebulae.

Though when at business Isaac Roberts worked with unremitting diligence and pains, he still found time to supplement an education which, in his earlier years, had been somewhat scanty. The result was that he became a recognised master of his craft as a builder. Roberts was indeed, so much esteemed by his associates that his aid was frequently invoked as arbitrator in disputes where technical matters in building were involved.

At the commencement of his scientific work Roberts devoted himself principally to geology. The first paper he wrote was in 1869 on the Wells and Water of Liverpool, and in the following year he became a Fellow of the Royal Geological Society. In 1878 he read a paper at the British Association on the Filtration of Water through Triassic Sandstone, and it was in this year that he commenced his career as a practical astronomer.

As to the astronomical equipment with which Dr. Roberts accomplished his work, reference may be made to the interesting account given by Mr. W. S. Franks in "The Observatory," for August, 1904. Roberts commenced practical observations in 1878 with a 7-inch refractor by Cooke, which was erected at his residence, 26, Rock Park, Rock Ferry - the same home, it may be noted, which Nathaniel Hawthorne occupied when American Consul at Liverpool. In 1882 he moved his residence to Kennessee, Maghull, near Liverpool. In 1883 Roberts tells us that he made experiments in photographing stars with ordinary portrait lenses, varying in aperture between 3/8ths of an inch and 5 inches. The most efficient of these was one of 2 inches aperture by Lerebours & Secretan, and he used this as a standard for comparison with the others. The comparisons were made by attaching the cameras to the declination axis of the 7-inch refractor, and taking simultaneous photographs of well-known groups of stars under precisely similar conditions.

But the great step which he made may be given in his own words ("Monthly Notices" of the Royal Astronomical Society, January, 1886):- "The result of these experiments, and comparison with Mr. Common's great photograph of the nebula in Orion, was that I gave Sir Howard Grubb an order to make me a 20-inch silver-on-glass reflector, with 100 inches focal length, the photographs to be taken directly in the focus of the mirror, to obviate any loss of light by a second reflection, the photographic telescope to be mounted on the same declination axis as the 7-inch refractor, one being the counterpoise to the other." In a foot-note he adds that- "To Dr. Huggins is due the credit for devising this most ingenious, simple and useful mode of mounting a reflector and refractor side by side; and the skill of Sir Howard Grubb is well shown in the arrangements of the instruments to perform the objects intended."

Mr. Franks records that "over a year was spent by Dr. Roberts in minor alterations and perfecting details before the instrument could be considered good enough to perform satisfactorily the work which was expected of it. From that day to this - with the exception that a Calver mirror was substituted for the Grubb in 1888 and a 5-inch Cooke camera added in 1895 - the equipment remains the same as originally planned by Dr. Roberts, a fact which speaks for itself as to the patient forethought bestowed upon this pioneer instrument, which has now become historically famous."

One circumstance, however, it would ill become the present writer not to record. Before ordering the 20-inch telescope from Grubb, Dr. Roberts had obtained an 18-inch instrument from the same maker. The results were so encouraging that he decided to enlarge the equipment on the same principle as above mentioned. The 18-inch telescope thus displaced, presented by Dr. Roberts to the observatory of Dunsink, co. Dublin.

As to the relative merits of reflectors and refractors for celestial photographic work, there has been much controversy, and in this controversy Roberts, as might naturally be expected from his great success, vigorously upheld the claims of the reflectors. As Mr. Franks tells us, "Roberts was one of the earliest and most consistent advocates of the merits of the reflector for celestial photography, and lived to see his predilection confirmed in quarters where there had previously been a strong prejudice for refractors. His views on the relative performance of camera lenses are well known, but it is not so well known that he had a very perfect star-camera fixed on the tube of the 20-inch reflector, with which all objects were photographed in duplicate, during the last nine years; and it was the unvarying superiority of the reflector plates that made him so sceptical as to much that was called nebulosity on camera plates by other observers."

The climatic conditions of Maghull did not admit of as many clear nights as an enthusiastic astronomer would desire; accordingly Roberts, after freedom from the cares of business had rendered a change of residence possible, determined to move his observatory to some more favoured locality. He took characteristic pains to make his change effectual. He personally investigated many sites. He even went out to the West Indies to see whether he could there obtain the conditions that seemed to him best. Finally he decided to establish his observatory on Crowborough Hill, Sussex, and, as the event proved, no choice could have been more judicious.

To Crowborough the astronomical equipment was transferred in 1890, and there, with unremitting diligence, the work was carried on, so that thousands of negatives have been taken and carefully preserved as the result. Starfield, as his house at Crowborough was called, was an ideal home for an astronomer. At an eminence of 800 feet, it commands a superb view over the surrounding country. The observatory was in communication with the commodious residence, and situated in a beautiful garden. To this garden Dr. Roberts devoted much care and attention. The visitor to Starfield could not fail to be impressed by the wonderful gallery of astronomical photographs there displayed. The plates of comets, of star clusters, and above all, of nebulae, judiciously selected from the thousands available, formed a magnificent exhibition on the walls.

The astronomical work of Dr. Roberts at Crowborough was carried out with systematic thoroughness. The time tables, according to which the day was passed, gave to each hour its allotted task. Some hours of the morning and some of the afternoon were always set apart for astronomical work. In the early years of his career at Maghull he was himself the capable photographer of the heavens. At Crowborough he was so fortunate as to secure the skilful services of Mr. W. S. Franks as his practical photographer, and it was by the diligence of Mr. Franks, under the incessant supervision and guidance of Dr. Roberts, that the wonderful collection of Crowborough photographs has been obtained.

How diligently the work was carried on from year to year will, perhaps, be best seen by looking at the successive Annual Reports of the Council of the Royal Astronomical Society. To these Reports Dr. Roberts contributed each year an account of the work done in his observatory during the preceding year. Of these reports there are about twelve. The last but one, dated February, 1903, gives a list of about seventy nebulae which had been photographed during 1902. The photographs were taken with the 20-inch mirror, which had been recently re-silvered, and the length of exposure was generally 1½ hours. In this year, as in others, the principal comets which appeared were also photographed.

The last of these notable lists, dated February, 1904, contains a magnificent record of work. There are upwards of ninety entries. The great majority of the objects photographed are nebulae, as in the former lists, but a good many clusters, or parts of the milky way, are included, and occasionally some other objects, such as the famous star (1830) Groombridge, and the comet of Borelly, in 1903.

In the words of Roberts himself he "has contributed to the Royal Astronomical Society and to Knowledge,' between the years 1886 and 1903, upwards of 150 photographs taken with his 20-inch reflector, each of which showed structural and other details of objects in the sky, that were previously unknown to astronomers." The last words make a great claim, but its complete justice will be admitted.

Much labour was devoted by Dr. Roberts to the design and construction of an instrument which he called the Pantograver. The object of this instrument was to transfer, as it were, the images of stars, both in size and positions, from a perishable gelatine film to an imperishable record, by engraving them on a copper plate. But this machine originated in the early years of Dr. Roberts' astronomical work, and before the time when he had fortunately decided to devote himself to the photography of nebulae. It was at first Dr. Roberts' intention to prepare a photographic chart of the heavens on a scale twice the size of Algilander's, and with an exposure of 15 minutes for each plate, and several specimen plates were sent to the Royal Astronomical Society in 1886. After the international scheme had been formed by the Convention in Paris for the preparation of the photographic chart of the heavens on a vast scale, Roberts saw that his energies could be most effectively employed in some other direction than that of charting stars, and thus the Pantograver has had but little relation to his later work. For a description of this machine reference may be made to his paper `On an instrument for measuring the positions and magnitudes of stars in photographs, and for engraving them upon metal plates, with illustration of the method of using the instrument.' "Monthly Notices," vol. xlix., p. 5.

The Gold Medal of the Royal Astronomical Society was awarded to Dr. Isaac Roberts in 1895 for his photographs of star clusters and nebulae. The address on the presentation of the medal was delivered by the President, Sir W. de W. Abney, whose profound acquaintance with the photographic arts, made the occasion one of exceptional interest. In this address Sir W. Abney says:-

"The photographs by Common of the Great Nebula in Orion were epoch-making in astronomical photography, and worthily was the medal bestowed on him for his classic work, and it is no disparagement of the labours of the present recipient (Roberts) if one traces in them the mark of what Common had shown to be possibilities."

Perhaps the most famous of Dr. Roberts' photographs was that of the great nebula in Andromeda. This plate it was which first fully illustrated the capabilities of photography for the representation of nebulae. Even after the lapse of 15 years it may still be doubted whether any more beautiful representation of any celestial object has ever been produced. Of this Sir W. Abney said in the address just referred to:-

"In December, 1886, Roberts produced a photograph of the nebula in Orion with his 20-inch reflector with an exposure of 15 minutes, and almost exactly 10 years after he produced a photograph of the same object with an exposure of 81 minutes, and introduced us to nebulosities in the surrounding parts which were unsuspected before. . . . A little afterwards he produced his recently published photograph of the great nebula in Andromeda, giving an exposure of 4 hours to the plate. In this prolonged exposure we have an example of a triumph of patience and instrumental perfection, though these qualities are exhibited in other instances as well. This beautiful object is depicted with rings of nebulosity in great perfection, and we can correct the eye observations which had previously been made upon it. The stars in the field are beautifully sharp and round, showing that the eye as well as the instrument had to be employed throughout that long exposure to correct changes in the position of the star due to atmospheric refraction, and variation in the rate of clock-driving."

Notwithstanding all his later successes with the spiral nebulae, Roberts always considered the Andromeda picture as his most notable achievement. In the fine portrait of him which was executed shortly before his death by his wife's sister, the favourite pupil of Rosa Bonheur, Roberts is represented resting in an armchair, and holding in his hand one of his memorable photographs. The plate which he chose was that of the great nebula in Andromeda, taken 15 years before. With consummate skill the artist has reproduced in an oil painting much of the delicacy and beauty which gave that picture its charm.

In 1896 Dr. Roberts was one of the party who went to Vadso in the steamship "Norse King" to observe the total eclipse of that year. The eclipse itself was disappointing, but the circumstance record from the fact that among those on board was Mademoiselle Dorothea Klumpke Roberts, D.Sc., of Paris Observatory, herself an earnest and distinguished worker in astronomical science. The acquaintance thus begun had a happy issue. In 1901 Roberts married for the second time, and in this union with his fellow-traveller on the "Norse King" Isaac Roberts found not only domestic affection, but also the happiness of sympathetic co-operation in his notable work. His first wife, to whom he had been married in 1875, was Ellen Anne, daughter of Mr. Anthony Cartmel.

The chief public testimony to the value of Dr Roberts' work is found in the facts that in 1890 he became a Fellow of the Royal Society, that in 1892 he received the honorary degree of D.Sc. from the University of Dublin [Trinity College, Dublin] on the occasion of its tercentenary, and that, as already mentioned, he received the gold medal of the Royal Astronomical Society in 1895. When he left Liverpool for Crowborough he was presented with an address signed by the Mayor of Liverpool, the leading citizens, and many scientific men connected with the University College in that city. In Crowborough he was highly respected for his vigorous independence of thought. Though he did not come prominently before the public as a politician, he held exceedingly strong views on many public questions. He was an enthusiastic Free Trader, and a sturdy opponent of the recent Education Acts.

His death took place quite suddenly on July 17, 1904. He had been working at his negatives on the very last day of his life, only a few days after he attended the funeral of his old and valued astronomical friend, Captain Noble.

His estate of £40,000 he bequeathed for the provision of the annuities to his widow and other relatives, the capital ultimately to go to the Universities of Liverpool and Wales for the foundation of scholarships.

Roberts' photographs will gather increased value as time advances. The changes in the nebulae, if changes there be, can be only certainly ascertained by the comparison of the photographs separated by long, perhaps very long intervals of time. The magnificent plates have been bequeathed by Dr. Roberts to his widow, Dorothea Isaac Roberts. In her most capable hands astronomers know that nothing will be omitted which zeal for the advance of astronomy and affectionate reverence for the memory of the dead can suggest.

The best memorial of Isaac Roberts is to be found in his two magnificent volumes of "Celestial Photographs," which he generously distributed widely among astronomers. We conclude with an extract from the preface to Roberts' first volume in 1893, which he himself quoted from in the preface to his later volume in 1899. The dignity of the words illustrates the character of the man as well as the importance of his work-

"It has been my aim, in publishing the photographs and descriptive matter contained in the following pages, to place data in the hands of astronomers for the study of astronomical phenomena, which have been obtained by the aid of mechanical, manipulative, and chemical processes of the highest order at present obtainable, and tat such data should be, as regards the photographs, free from all personal errors.

"The photographs portray portions of the starry heavens in a form at all times available for study, and identically as they appear to an observer aided by a powerful telescope and clear sky for observing.

"Absent are the atmospheric tremors, the cold observatory, the interrupting clouds, the straining of the eyes, the numbing of the limbs, the errors in recording observations, and the many hardships incurred by our predecessors of glorious memory in their attempts to see and fathom the illimitable beyond.

"I commend the observations and the photographs herein to astronomers and students of the new astronomy."

R.S.B.

Further reading

• An article about Isaac Roberts by Michael Hoskin in the Dictionary of Scientific Biography (edited by C. Gillispie, published by Charles Scribner's Sons, New York).
  
  
• An article Discovering M31's Spiral Shape by the distinguished astronomer Gérard de Vaucouleurs appeared in the Sky and Telescope magazine in December 1987 (pages 595-598). It is centred around the discovery of the spiral nature of the Great Andromeda Galaxy by Isaac Roberts.
  
  
• An article Dr Isaac Roberts (1829-1904) and his observatories by Stephen James appeared in the Journal of the British Astronomical Association, vol. 103, pp. 120-122, 1993. A letter by A. F. Edwards about the mirror of the 20-inch telescope was written in response to this article, appeared in the Journal of the British Astronomical Association, vol. 103, p. 218, 1993.
  
  
• The Liverpool Astronomical Society has published a short pamphlet (with four pages of text) called Isaac Roberts by Stephen Hughes (1994) as part of its North-west Astronomers series of booklets. It gives a useful overview of Roberts's scientific work. (A brief review by D. Wright appeared in The Observatory magazine, Vol. 115, No. 1126, p. 153, June 1995.) The booklet can be ordered from the Liverpool Astronomical Society for £1.50, plus postage.
  
  
• The popular magazine Astronomy Now carried an article One of the First Astrophotographers about Isaac Roberts, written by F. White, in a special feature about astronomers of the Victorian era (Astronomy Now, vol. 11, pp. 41-53, May 1997).
  
  

Web resources

• A biographical article by Philip Pennington about Isaac Roberts.
• A scanned copy of Stephen James's article Dr Isaac Roberts (1829-1904) and his observatories from the Journal of the British Astronomical Association can be found at the NASA Astrophysics Data System.
• A letter by Robert Katz about the current state of the 20-inch telescope at the Science Museum, published in the Journal of the British Astronomical Association (107, 345, 1997).
• Pictures and discussion of Isaac Roberts's memorial in Flaybrick Cemetery, Birkenhead (with information about the cemetery).