X-ray photographs of the tongue positions of Jones' cardinal vowels [i, u, a, ɑ] (adapted from Jones 1972: frontispiece).

• The photographs are of Jones' mouth during vowel production.
• Jones writes: "A chain of small lead plates strung together was placed on the tongue to show its outline. The large dot added on each photograph marks the highest point of the tongue. The cross is a point of reference (near the end of the hard palate).... The photographs were taken by Dr. H. Trevelyan George in St. Bartholomew's Hospital, London, in January, 1917". And on p. 32: "They were taken ... by Dr. E. A. Meyer's method of placing a very thin metal chain on the tongue. They were first published in the Proceedings of the Royal Institution, Vol. XXII, Part 1, Oct., 1919. The originals may be seen in the Department of Phonetics, University College, London, W.C.1."
• For this image, Jones' large dots are overlaid with large red dots to aid the viewer.
• Jones' photographs are in the public domain in the United States.