Grace's Guide

British Industrial History

Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 133,744 pages of information and 211,898 images on early companies, their products and the people who designed and built them.

Henry Cort Harold Carpenter

From Graces Guide

Jump to: navigation, search
1918.
1935.
1940.

Professor (Henry Cort) Harold Carpenter (c1875-1940), M.A.

H. C. H. Carpenter. Professor of Metallurgy, Royal School of Mines.

Books:

  • "Metals," (in collaboration with Dr. J. N. Robertson).

1940 September 15th. Died age 65


1940 Obituary [1]

The unexpected death on September 13, 1940, of Sir Henry Cort Harold Carpenter, MA., Ph.D., D.Sc., D.Met., F.Inst.Met., F.R.S., as a result of an accident in South Wales, came as a great shock to his many personal friends and to the large number of his admirers amongst the technical and scientific men in all parts of the world. This is a serious loss for this country to which he was so proud to belong; to the science of metallurgy, for the advancement of which he made so many valuable contributions; and to all who had the privilege of having worked, or having been closely associated, with him. By his death an important link in the chain of metallurgical teaching and research is broken, for he came into the subject at that rather vital stage when physical chemistry and physics were being more intensively applied to the study of metals and their alloys.

From 1902 up to the time of his death, he played a very prominent part as a teacher, as an original investigator, and as an organizer, in extending the boundaries of his subject and strengthening the scientific foundations on which it rests. In an unusual degree Carpenter possessed those qualities which generated in others a profound respect, admiration, and personal regard for him. These feelings always developed spontaneously and were not due to any obvious desire on his part to cultivate them; they grew as a result of his natural modesty, transparent honesty, and keen sense of justice, all of which were outstanding features of his character. He always displayed deep interest in the work and careers of younger people, and derived much pleasure in helping and encouraging them in their work and aims. If, however, as sometimes happened, he did not feel justified in supporting a claim, or subscribing to a particular point of view, he had an effective but charming way of conveying his own impressions. This was done, not so much by what he said as by what he left unsaid, and he thereby led others to get an unbiased opinion of any situation.

In spite of this apparent hesitation, he was a man of great determination and strong convictions, though he rarely showed any wish to take part in controversies. He was always far more interested in discovering new facts and collecting or collating evidence which he used to guide his thoughts and actions. He found no pleasure in building temporary theories on insufficient or flimsy evidence. As the grandson of Dr. W. B. Carpenter it is not surprising to find that he revealed an early interest in, and aptitude for, science; and, as the great-grandson of Henry Cort (the inventor of the puddling process for making wrought iron, and the introducer of grooved-rolls), it seemed particularly appropriate that he should turn his scientific talents to the study of metallurgy. His father was an engineer, one of a small body of men who took an active part in arranging for and giving lectures during the early days of the adult education movement. In this connection, Carpenter derived much boyish pleasure in assisting his father to prepare lantern slides; this, in some degree no doubt, explained his deep sympathy for all enterprises which aimed at impeding the conditions of the masses. Owing to the comparatively early death of his father, his character was greatly influenced during the formative period of his life by his distinguished uncle, Dr. Estlin Carpenter. In this connection, Professor Soddy writes:

"My intimacy with him brought me to know well his distinguished theological uncle - Dr. Estlin Carpenter - who was for a long time closely connected with, and for some years Principal of, Manchester College, Oxford. A saintly man with a leonine head and physique, and an authority on oriental religions. To him and his delicate (not to say sylph-like) consort, who was a daughter of the Buckton of testing-machine fame, Carpenter undoubtedly owed much, for he was under the guardianship of these two rare spirits during his early youth. They were, no doubt, responsible for his keen love of nature, walking, climbing, and his great appreciation of the beauties of the country-side and scenery of all kinds."

Carpenter went to Eastbourne College in 1892, and thus had the good fortune to have as his science master a brilliant young Welshman, R. E. Hughes (just down from Jesus College, Oxford, where he had held a science scholarship gained from the University College of Wales, Aberystwyth), whose chief scholastic interest was in the training of boys for science scholar- ships at Oxford. Carpenter gained the Science Postmastership at Merton College, Oxford, in 1893.

Whilst at Eastbourne he struck up a very close and permanent friendship with Frederick Soddy (later to become so eminent as a Professor of Chemistry). This association was renewed when Soddy went to Oxford, and again when they were students in Germany. Carpenter took a First-Class Honours degree at Oxford in 1896 and, at the end of the summer term, he and Soddy proceeded to Germany for the purpose of learning the language so that the former could take up his studies at the University of Leipzig at the beginning of the following session. Soddy says:

"We spent the summer most profitably and enjoyably at Jena, though we were never inside the University or the famous Schott Works, he studying the language seriously and I reading chemistry in German textbooks. His winning ways secured him an vatic into one very select Jena circle—for every day he was coached, quite gratuitously, in conversation and the niceties of German etiquette, by a mysterious old lady I never saw: for it was part of the bargain I should not come, as I had put myself for ever beyond the pale by sitting on the sofa when we first arrived at our pension. "Thoroughly grounded in the language, he proceeded to Leipzig, where he studied for two years and achieved the distinction of being the first foreigner, at Leipzig or at any German university, to obtain the Ph.D. degree 'summa cum laude.' His work was in organic chemistry, which may seem curious to subsequent generations, but, as a matter of fact, was the case with many of that period who subsequently rose to eminence in other branches of science."

After Leipzig, Carpenter went to Owen's College, Manchester, to work with W. H. Perkin, and it was not until 1902 that we get the first glimpse of any indications of a transfer of his interests to what later became known as physical metallurgy. It was at this stage that he was appointed as head of the two new departments of chemistry and of metallurgy at the National Physical Laboratory, Teddington. In those early days the various departments were almost completely accommodated within Bushey House, the old chapel being converted into the chemistry laboratory, and the metallurgical department consisting of what had been originally the kitchen and part of the servants' quarters. By about the beginning of 1905, Carpenter's interest had become entirely centred around metallurgical research, and he then severed his official connection with chemistry.

He left Teddington in the autumn of 1906, but, in those few years that he was there he was responsible for a remarkable amount of high-quality work. A clear indication of the volume, range, and standard of his researches during this time can be gained by reference to the papers that were published under his name.

His first metallurgical publication was in collaboration with the late B. F. E. Keeling. This dealt with the determination of the freezing-point ranges and other thermal transformations in the iron-carbon system. Those acquainted with the many experimental difficulties connected with work of this kind, recognize, with some surprise, that they were so completely overcome nearly forty years ago by these investigatorjs. Carpenter and Keeling not only satisfactorily attained the necessary temperatures, which was no small achievement in a laboratory in those early days, but they successfully guarded against the introduction of errors from thermocouple contamination and numerous difficulties associated with the control and correlation of the chemical composition with the thermal data. Some idea of the outstanding merit of this work may be gathered from the fact that it has stood the test of careful scrutiny by many subsequent workers who have bad far more elaborate resources and equipment at their disposal. It is interesting to know that their data gave some indications of the change corresponding with the 8 range of the system and of the decreasing solubility of carbon in cc iron at temperatures below the carbide change point: features that were not even suspected until many years later.

Carpenter's next research dealt with the study of high-speed tool steels, with special reference to the influence of tungsten, molybdenum, and chromium upon the thermal critical points of steel after heating to various initial temperatures. The results were embodied in two papers and, for the first, he was awarded the Carnegie Research Gold Medal. Much new and useful information was brought to light in these papers concerning the functions of the above- mentioned elements, which formed the basis upon which many later investigators worked.

Most of Carpenter's other researches and work, from the early part of 1904 up to the time he left Teddington in the late summer of 1906, were concerned with two extensive investigations which were incorporated in the volumes of the 7th and 8th Reports of the Alloys Research Committee of the Institution of Mechanical Engineers. The first of these was on steel; it covers such a complex field that it is virtually impossible to do justice to its value without taking up more space than can be spared in this notice. It can, however, be said that the report contains a mass of data which were quite new at the time, and which have been extensively used by other workers. The 8th Report is a comprehensive study of the properties of the copper-aluminium alloys. The writer had the good fortune to be associated with this work, and has always looked upon that period as being the happiest and most profitable in his experience. It was a great joy to be brought into intimate contact with a man possessing Carpenter's sterling qualities and ability combined with such an abundance of human sympathy and kindness; and it was an inspiration for any young man to be brought under his influence, and to have the opportunity of seeing how methodically he planned his work and how systematically he carried it through. There was no sign of hurry or bustle, and the atmosphere around him always remained calm and undisturbed. This, no doubt, accounts for his life having proved unusually productive, both in the quantity of the work carried out, and the standard of the results obtained.

The provisional plans for this work on copper-aluminium alloys were formulated by Carpenter in May 1905, but it was a month or two later before it was possible to commence the experimental observations. The investigation represented a complete survey of the properties of the alloys in the cast, rolled, and heat-treated conditions, and the report on it has since proved to be a standard work of reference. Some idea of the magnitude of the undertaking can be gauged from the fact that the publication covered over 200 pages of the Journal of the Institution of Mechanical Engineers. In addition, there was an appendix which gave a fairly accurate forecast of the essential features relating to the constitution of the system. Looking back, the writer is even now amazed at the facility with which Carpenter managed to marshal the enormous amount of data contained in the report, and the clear and readable form in which the results are described and discussed. It took him a remarkably short time to do the whole of this. Each morning he settled down to the task immediately after attending to his correspondence, and worked steadily on without a break, except for a short lunch interval. He rarely destroyed a sheet of paper, but on the few occasions when a correction was necessary it was neatly inserted in red ink. The procedure was typical of the man, for he had an exceptionally clear mind, and this, coupled with an easy-flowing style of writing, make all his publications attractive reading.

The impressions it is desired to convey in this connection have been delightfully described in a notice by Dr. S. W. Smith:

"By the grace and polish of the spoken word and by his pen, he adorned the profession of metallurgy in a way to which none of his contemporaries could aspire. Beneath a modest reserve there lay a firmness in decision and, to those Who knew him well, a keen enjoyment of his work and a subtle sense of humour which evoked an almost boyish response to any playful reflection or incident which arose whether in committee or in personal conversation."

Whilst at Teddington he carried out another interesting piece of work dealing with the embrittlement of nickel wire when used as the heating element of resistance furnaces. A paper on it was read before the British Association for the Advancement of Science in 1906 and was later published in Engineering. The deterioration of the wire, he found, was due to the liberation of gases during repeated heating and cooling, which was accompanied by a strong tendency to develop fibrous crystals along the length of the wire; these could be easily separated from each other almost like strands of string. Although there was no obvious connection between this discovery and his later epoch-making researches with Miss Elam on the growth of large crystals of aluminium, it may have been partly responsible for his study of that problem.

In the summer of 1906 he was invited to occupy the newly created Chair of Metallurgy at the Victoria University of Manchester. This he accepted, and took up his new duties in October of that year. He was thus given the opportunity for which he was looking a reasonable amount of time to pursue his researches, with complete freedom to turn his attention in any direction he wished, and, at the same time, an opportunity of increasing the influence he could bring to bear on students of his subject. His success as a teacher is clearly revealed by the large number of his old students who now occupy prominent positions in the academic and industrial worlds of metallurgy.

In October 1905, about a year before he left Teddington, he married Miss Ethel M. Lomas, who was his devoted and constant companion for the rest of his life. Lady Carpenter was keenly interested in all her husband's work and was often present when he gave papers at meetings of the various societies. She was a source of great encouragement to him, and, on all suitable opportunities, he paid tribute to her for the loyal support she gave him. This was especially noticeable on the occasion of his receiving the award of the Bessemer Gold Medal of the Iron and Steel Institute in 1931.

Carpenter was Professor of Metallurgy at Manchester from 1906 until the end of 1913. During these years he built up the department from zero, and under his inspiring guidance this school quickly became known as a flourishing centre of research. In spite of being called upon to serve on numerous committees and to give much time to problems relating to university affairs, and in spite of the fact that, for some time, he did not enjoy perfect health, he found time to help and direct the researches of students and do a considerable amount of research work himself. This is evident from the publications which came from the department under his name alone or jointly with others. The first of these was one dealing with the complex problem of the growth of cast iron after prolonged heating or repeated heating and cooling. Prior to his work with Rugan on this subject, a great deal of confusion existed concerning the cause of the growth of cast iron, and many complicated suggestions had been advanced to explain the various phenomena. Some of these were within the bounds of possibility; others could scarcely be described in that way. The problem was one of considerable commercial importance in many industrial directions, and it was rather forcibly brought into prominence as a result of the great fire at San Francisco. It was found there that wherever cast iron had been extensively used in the construction of large buildings the walls were completely ruined because the east-iron supports, &c., became permanently elongated and distorted and, in consequence, would not contract with the masonry on cooling. The fundamental causes of this trouble were carefully examined by Carpenter and Rogan. The primary cause of growth was found to be duo to the oxidation of the iron by penetration of oxygen to the interior through the flakes of graphite disseminated in grey cast iron. The authors demonstrated how this was affected by many other variables, and thus laid down the principles along which improvements might be brought about. Many instances could be cited where the results of this work have been applied with considerable success.

Another investigation having direct practical applications was that relating to the production of non-rusting castings to withstand hydraulic pressure. In many respects this was a natural development of the previous work on copper-aluminium alloys, for it was, to a large extent, confined to an examination of how the 90 per cent. Copper-10 per cent. aluminium alloys behaved in this connection. For a long time the results were most discouraging and disconcerting because they were so erratic; sometimes a casting would be obtained which would withstand a pressure of 18 tons/in.2, whereas others would let the water through at an extremely low pressure. It was, however, ultimately discovered that success or failure depended upon the control of small details of procedure during the operation of teeming. When the necessary precautions were taken to prevent an accumulation of films of alumina within the body of the casting, good results were obtained. Again, about this time, we get another foretaste of Carpenter's keen interest in the behaviour of metallic crystals and the various means whereby they can be made sensitive to growth. This was revealed by his work on the "Re-crystallizing Properties of Electrolytic Iron in the Form of Thin Strips on Being Heated or Cooled Through the A, Change-Point." Thus he found that, by this treatment, when using material of certain critical ranges of thickness, he obtained phenomenally large crystals. Whilst he devised means of controlling the character of this growth, he was, unfortunately, unable to obtain crystals that were large enough for the study of their individual properties. The experience he gained in this connection, however, no doubt proved useful to him later on, and it certainly increased his desire to obtain crystals large enough for a study of their mechanical and other properties. There followed the careful determination of the freezing-point ranges and other changes of constitution of the aluminium-copper-zinc alloys containing the a, 8, and y constituents of this ternary system. Another interesting publication about this time (1911) related to the re-discovery of the thermal critical point which occurs at about 4'70° C. in the (3 constituent of the copper-zinc alloys. No notice had been taken of this for many years, and it was not included in the equilibrium diagram of the system.

This paper was followed by others which aimed at finding an element which would accelerate the p change, and thus provide a more definite indication of the inner meaning of the transformation. These researches led many other workers to turn their attention to this rather fascinating subject. Still another paper dealt with a careful study of the constitution of the silver—zinc alloys, and in this many interesting suggestions were advanced concerning the striking similarities that exist between the constitutional diagrams of copper or silver and their alloys with other elements.

In 1908, Carpenter and the late W. H. Johnson discussed together the desirability of forming an Institute of Metals, which would have as one of its chief objects the provision of meetings for the discussion of original researches dealing with non-ferrous metals, &c., and a journal in which they could be published. After much pioneering work had been done amongst influential men whose co-operation would have considerable influence in making a success of this proposal, it was decided to take further steps by advertising the scheme and calling a meeting for the purpose of gauging whether it would meet with sufficient support. Before this was done, however, Carpenter devoted a great deal of time and energy to persuading many people to "give it their blessing" and, as the result of his earlier work for the Alloys Research Committee, he was able to procure the assistance of such men as Sir William White, Sir George Beilby, Sir Gerard Muntz, Mr. Leonard Sumner, Mr. F. Tomlinson, and others. He was also instrumental in overcoming active opposition in some quarters and considerable apathy in others. In due course a meeting was called at the Midland Hotel, Manchester. Sufficient enthusiasm being displayed at this meeting, a corresponding one was held in Birmingham, but there was still no guarantee of success. During this early period, Carpenter acted as Honorary Secretary and was, therefore, in the best possible position to realize that the ultimate success of the Institute would largely depend upon the ability and personal qualities of whomsoever was appointed as permanent secretary. He and his colleagues gave much attention to this and were delighted when Mr. G. Shaw Scott was appointed in 1908. When informing the new Secretary of his appointment he said: "Mr. Shaw Scott I have to inform you that the Council has just appointed you the first Secretary of the newly formed Institute: it is up to you to see that it goes!". The continued progress of the Institute and its present high status is sufficient justification for Carpenter's confidence in the new Secretary.

He continued to give unstinted support to the work of the Institute of Metals and served as Honorary Secretary for the years 1908 to 1910, as Vice-President from 1911 to 1918, and as President from 1918 to 1920. He was elected a Fellow in 1929 and returned to the Council in 1939. He also acted as Chairman of the Corrosion Committee, and the investigators greatly appreciated the keen interest he displayed and the stimulating advice he gave them in their work.

In the late summer of 1913, he was appointed to the Chair of Metallurgy at the Royal School of Mines, London. He fully recognized that going to London would place many additional burdens and responsibilities on his shoulders, but that it would also give him more opportunities of serving his country by giving his advice and the benefit of his extensive experience and sound judgment to the large number of Government committees upon which he would be called to act. He was always ready to do what he could in this way, and never spared himself, quite unselfishly helping forward the work of any committee on which he served. He was remarkably effective in business of this kind, for he possessed an almost uncanny way of gauging what steps should be taken, and had a very clear vision of how to proceed and of how to gain the support of others. This was done with such ease and grace as to seem to call for little effort on his part, but, in fact, it was the result of much patient thought and careful preparation. From another point of view, going to the School of Mines gave him considerable satisfaction, if only because the post had once been held by that very distinguished metallurgist, Dr. Percy.

Carpenter left Manchester towards the end of December 1913, but before starting on his new work he made a six months' tour of the metallurgical works and centres of research in the United States of America and in Canada. This was a strenuous undertaking, especially in view of the extensive area he covered and the fact that he was alone and had comparatively little time in any one place. It was, however, a useful and profitable experience he gained much valuable technical information from it, and retained man); interesting recollections of the people he met.

He took up his new duties at the Imperial College in October 1914. The war seriously interfered with normal plane and academic work and life, and Carpenter was called upon to give advice on metallurgical problems of various kinds directly arising out of the war. He was, however, also able to turn his attention to some necessary re-adjustments in the working arrangements of his department, in preparation for the end of the war, as well as to find a limited amount of time for research.

In collaboration with L. Taverner, Carpenter published in 1917 a very complete study of the influence of annealing temperature on the rate of softening of cold-rolled aluminium sheet. This was a highly meritorious investigation in itself and contained a mass of new evidence, but it was even more important and significant in that it can be regarded as the foundation of his researches with Miss Elam on single crystals which will be referred to again.

An outstanding piece of historical research on the "Progress of the Metallurgy of Copper" was incorporated in a series of Royal Society of Arts Cantor Lectures delivered in December 1917; these lectures were published by the Society early in 1918, and should be read by all students of metallurgy and industrial history. They clearly reveal the progressively increasing tendency towards the application of science to this particular industry, and the historical aspects of the effect of the commercial side upon its growth and its relative decline in this country. It is significant to note how a short-sighted financial policy concerning the method of purchasing raw material led to a more rapid decline of the copper-smelting trade in Great Britain than would have occurred had a more enlightened system been adopted.

After 1918 Carpenter settled down to a period of nearly 22 years' metallurgical work which was evenly apportioned between teaching, research, acting in an advisory capacity on important Government committees, and unremitting service to the three chief metallurgical societies.

Besides occupying the presidential chair of the Institute of Metals, he was President of the Institution of Mining and Metallurgy for 1934, and of the Iron and Steel Institute for 1935 and 1936. For some years he acted as Honorary Treasurer of the Iron and Steel Institute, and was closely associated with the effort that brought that Institute and the Institute of Metals into a common home in Grosvenor Gardens. His advice was a source of great help to the permanent secretaries of these Societies. His election as a Fellow of the Royal Society in 1918 gave great pleasure to all his metallurgical and engineering friends, because the high quality of his work was universally recognized. It is not proposed to give a complete catalogue of Carpenter's many Publications from 1918 onwards, as this would take up too much space. They were very numerous and covered a wide range of subjects. They include papers dealing with the crystal structure of native copper, the formation of ferrite from austenite, the aestenite—pearlite inversion, and many others.

It was in 1920, that the first of a number of papers with Miss Elam was published on the production of single crystals of aluminium and the study of their mechanical properties. Present and future metallurgists will always look back upon these re- searches as representing the beginning of a new era in metallography. It was a brilliant achievement to have so systematically and completely determined the precise conditions necessary to make the millions of crystals present in a polycrystalline mass sensitive, and change them to a common orientation of single crystals. As a result of this he and Miss Elam were able to make a careful study of the mechanical properties of single crystals of aluminium, and to observe their behaviour when subjected to plastic deformation. This had been, so to speak, the dream of metallurgists for many years, but it was left to Carpenter and Elam to transform the vision into reality. This work opened up quite new fields of study, and later investigators adopted the Carpenter—Elam method for other metals; in this way a large amount of experimental evidence bearing upon the properties of metallic crystals has been brought to light which was unattainable before their work.

Carpenter gave the Institute of Metals May lecture in 1926 on "The Production of Single Crystals of Metals and Some of Their Properties," and he gave the James Forrest lecture of the Institution of Civil Engineers in 1927.

He was a member of the Advisory Council of the Department of Scientific and Industrial Research for six years, and was Chairman of the Metallurgical Advisory Board of the Council for the whole period extending over many years until its work was completed a short time ago. He served on the Council of the Royal Society and on the Executive Council of the National Physical Laboratory. He was chairman of a Treasury Committee appointed to inquire into and report upon the conditions of professional employment in the public services. The Carpenter Report, which embodied the recommendations of that Committee, was the means of removing many anomalies and placing professional men in Government service on a satisfactory basis.

For his contributions to science and metallurgy, and his many varied services to his country, he was knighted in 1929. This was an honour which gave general pleasure and satisfaction to all who knew him and his work. Carpenter refused numerous invitations to write a book, and for years steadily declined to consider doing anything of this kind. Fortunately he was finally prevailed upon to change his mind, and, in collaboration with Dr. J. M. Robertson, produced the most comprehensive work dealing with the properties of metals that has ever been written in the English language. It covers 1485 pages, and for many years to come metallurgists and engineers will be grateful that he decided to leave them such a wonderful account of his thoughts and experiences in these two monumental volumes entitled " Metals." Amongst the many awards and distinctions he received may be mentioned the following :

  • Carnegie Gold Medallist of the Iron and Steel Institute, 1905.
  • Thomas Turner Gold Medallist of the University of Birmingham, 1928.
  • Bessemer Gold Medallist of the Iron and Steel Institute, 1931.
  • Gold Medallist of the Institution of Mining and Metallurgy, 1932.
  • Carl Lueg Laureate, Verein deutscher Eisenhiittenleute, 1937.
  • Gold Medallist of the American Institute of Mining and Metallurgical Engineers, 1938.
  • Platinum Medallist, Institute of Metals, 1939.
  • Honda Gold Medallist of the Institute of Metals, Japan, 1940.
  • Honorary A.R.S.M. Honorary D.Sc. (University of Wales).
  • Honorary D.Met. (University of Sheffield).
  • Corresponding Member Swedish Royal Academy of Scientific and Industrial Research.
  • Honorary Member American Institute of Mining and Metallurgical Engineers.
  • Honorary Member Societe nationals pour l'Encouragement de l' Industrie.

By Principal C. A. EDWARDS, D.Sc., F.R.S.


1940 Obituary.[2]

SIR (HENRY CORT) HAROLD CARPENTER, professor of metallurgy in the Royal School of Mines, London, whose death at the age of sixty-five occurred on September 13, was regarded as the leader of the metallurgical profession in Great Britain. He came from a family which produced several distinguished men, and in view of his career it is particularly interesting that one of his great-great-grandfathers was Henry Cort, whose inventions did so much to establish the position of England at the head of the iron industry in the eighteenth and nineteenth centuries. Carpenter, however, was not originally trained as a metallurgist. He studied chemistry at Oxford and Leipzig, and became research fellow and demonstrator in Owens College, Manchester.


1940 Obituary [3]

SIR HAROLD CARPENTER, F.R.S., who died in tragic circumstances at the end of last week, enjoyed a world-wide reputation as a metallurgist. He was the joint author with Dr. J. M. Robinson of one of the most important works on his own subject - "Metals," 1939 - and for twenty-five years was Professor of Metallurgy at the Royal School of Mines, South Kensington......[more]


See Also

Loading...

Sources of Information