FIRST EDITIONS OF TWO IMPORTANT PAPERS, J. A. FLEMING ON HIS FLEMING VALVE & CHARLES BARKLA’S FIRST IN-DEPTH PAPER SHOWING THAT X-RAYS SCATTERED BY VARIOUS ELEMENTS PRODUCED BEAMS OF CHARACTERISTIC PENETRATION.
In 1904, English physicist J. A. Fleming rectified wireless signals using a diode based on the Edison effect, the unilateral flow of current between two electrodes in a vacuum tube; this was the first known use of the Edison effect. Fleming called his invention an "oscillation valve" because it acted in similarly to a valve in a pump that allows gas or water to move in only one direction. Fleming had “discovered that thermionic emission could be used to create what is now called a thermionic or vacuum tube, a device that controls the flow of electric current. He patented the vacuum tube as a rectifier to replace the coherer for use in receiving wireless transmissions” (History of Physics: The Wenner Collection).
At a March 1906 meeting of the Physical Society, Fleming read the paper that makes its first appearance in print here, in this 1906 Philosophical Magazine. In it, he “outlines the design and use of devices for rectifying high-frequency oscillatory signals such ‘as are employed in the rectifying circuits of wireless telegraph apparatus’” (Davis, Science in the Making, 8). “Oscillations in the primary circuit, produced by an induction coil and two Leyden jars, generate Hertz waves which are detected some distance away by the secondary circuit. The valve rectifies this signal, as confirmed by the steady deflection of a mirror galvanometer. Fleming used this arrangement to investigate the effects of changing various features; he also experimented with different filaments in the valve (ibid). Fleming’s discovery “was later developed by others for a host of applications from sound amplification to electronic switching in digital computers” (History of Physics: The Wenner Collection).
ALSO INCLUDED IS A PAPER BY THE ENGLISH PHYSICIST CHARLES BARKLA. While at Edinburgh, he began his investigations with Roentgen’s newly discovered X-rays. “Barkla noticed that X-rays were scattered by gases and that the degree of scattering was proportional to the density and molecular weight of such gases. From these, he deduced that the more massive the atom (higher atomic weight), the greater the number of charged particles (protons) in the nucleus and the degree of scattering.
“This was the first time that a connection was made between the number of protons, the atomic weight and the position of an element in Mendeleev’s periodic table. This was definitely a move toward the development of the concept of the atomic number and the recognition of its importance in the ordering of the chemical elements in the periodic table” (Martini, The Story of the Atom and Chemistry, 690). By 1905, Barkla was able to clearly distinguish “between the properties of secondary radiation from heavy elements and those of the scattered radiation by lighter elements” (Authier, Early Days of X-ray, 5.7).
In 1906 [in this paper] Barkla does “his most intuitive thinking, [showing] that X-rays scattered by various elements produced beams of characteristic penetration. This was indicated by the degree of beam absorption by an aluminum sheet of standard thickness. At that time, there was no way to measure the wavelength of X-rays; therefore, Barkla had to make his assessment by the absorption on the aluminum sheet” (Martini, 690). Barkla was awarded the 1917 Nobel Prize and his discovery was later used by Henry Moseley to show that elements can be uniquely represented by their ‘atomic number,’ the charge of the nucleus. Item #819
CONDITION & DETAILS: London: Taylor & Francis. 8vo. Complete. [viii], 840, 8 plates. Ex-libris: blind (uninked) stamp on the title page; no other library markings. Tightly bound in contemporary three quarter leather with some scuffing at the edge and spine tips. Five gilt-ruled tooled bands at the spine. Gilt-lettered red and black morocco spine labels. Bright and clean within. Very good condition.