{"content":[{"text":"2","bbox":{"left":0.495462,"top":0.067941,"width":0.010084000000000037,"height":0.01578299999999999}},{"text":"terms in 1877, 1878 and 1879 Maxwell had as his only audience Fleming and a Mr. Middleton. \"On \n one or two occasions,\" Flemingsays, \"I remember Maxwell gave a university lecture to me as his \n only audience.\" \n Although perhaps hardly relevant to to-day's proceedings, there is a point to which I should like to \n refer, because it has always somewhat mystified me. Although he sat at the feet of Clerk Maxwell \n for two or three years, in his \"Elementary Manual of Radio-Telegraphy,\" published in 1908, \n Fleming says that, in the electromagnetic waves radiated from an aerial, if the electric and magnetic \n fields are plotted, a wavy line is obtained in each case, \"but the maximum of one curve coincides \n with the zero point of the other.\" He advises the reader to make a model with two pieces of \n cardboard placed at right-angles and on each card draw a wavy line, but so that the maximum point \n of one lies over the zero point of the other. \"One of these lines,\" he says, \"should be marked E and \n the other H.\" All this was corrected and the wavy lines brought into phase when the second edition \n of the book was published. But the seed had been sown, and in P. P. Eckersley's book, \"All About \n Your Wireless Set,\" we read \"Flip! the electric strain goes past; flip! the magnetic strain goes past.\" \n He refers the reader to Fleming's graphical illustration. More surprising, in Volume 1 of Stanley's \n \"Textbook of Wireless Telegraphy,\" published in 1919, he pictures the radiated fields being of \n different colours and refers to a red colour of electric strain giving place to a yellow colour of \n magnetic strain, and so on. It must be remembered that Fleming wrote his book 30 years after he \n had heard Maxwell's lectures, and that during most of this time electromagnetic waves formed no \n part of his mental activities. \n While at Cambridge in 1879, Fleming was awarded the Doctorate of Science of London University, \n and the following year he obtained the Cambridge Bachelor of Arts degree, with a first class in the \n Natural Science Tripos. He then stayed on for a year as a demonstrator in mechanism. In 1881 he \n was appointed Professor of Physics and Mathematics at the new University College of Nottingham, \n but he had only been there a few months when he obtained an appointment in London, which he \n said he was \"only too glad to accept.\" \n In 1879, while still at Cambridge, he had been appointed scientific adviser to the Edison Telephone \n Company, which was involved in litigation with the Government; now, three years later, in 1882, he \n was appointed \"electrician\" to the Edison Electric Light Company, of which John Hopkinson was \n the scientific adviser. In those days the word \"electrician\" had quite a different meaning from what \n it has to-day. In 1884 he went to America to discuss with Edison the difficulties of the electric \n lighting industry in England, which were largely due to restrictive legislation. This close link \n between Fleming and Edison is of importance in connection with the thermionic valve. Since the \n British Association meeting that year was in Montreal, he took the opportunity of going to the \n meeting, and he visited many of the cities of Eastern Canada. He then returned to New York and \n made a thorough investigation of the electric light industry in America, which he embodied in a \n report to his directors on his return to this country. \n Five years before this, in 1879, Edison had obtained a British patent for a carbon-filament lamp of \n high resistance. In 1884, the year of Fleming's visit to him, Edison exhibited at Philadelphia an \n interesting discovery which he had made the previous year: he had fixed in the bulb of a carbon- \n filament lamp a metal plate carried by a platinum wire sealed through the wall of the bulb, and \n found that if the metal plate was connected through a galvanometer to the positive terminal of the \n filament the galvanometer showed that current was flowing; but if the connection was made to the \n negative terminal, no current was indicated. This phenomenon was subsequently known as the \n Edison effect. \n Edison made practical use of the device, but not for telegraphy. He connected the lamp filament \n with a suitable adjusting resistance across the mains in the power station. When the voltage between \n the mains had the correct value the filament had a certain temperature and the current flowing","bbox":{"left":0.095462,"top":0.101196,"width":0.809282,"height":0.821721}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}