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Special Exhibition Label: '''Dear Harry...' - Henry Moseley, A Scientist Lost to War" (14/5/15 - 18/10/15)

Harry’s most important work was conducted with a complex experimental setup, requiring ingenuity in design and determination in operation. Several pieces of connected apparatus were used.


An induction coil (1) supplied high voltage to an X-ray tube (2), which was evacuated with a powerful mercury vacuum pump (not shown). Within the tube, electrons were fired at a sample of a chemical element, creating X-rays specific to that element. Having to make and break a vacuum between each experimental run slowed down the work, and increased the risk of leaks. To increase the speed of the experiment, Harry ingeniously used a trolley on a set of rails (3) to present a succession of elements without breaking the vacuum. Acquired from many sources, the elements were identified and stored in envelopes (4).


The X-rays were made parallel by passing through a slit (5) and into a cylindrical chamber, the spectrometer (6). In the centre of the spectrometer they struck and were deflected by a large mounted crystal of potassium ferrocyanide (7). Finally, the most characteristic X-rays were recorded photographically. For Harry, the crucial information was the angle of the X-rays, so the photographic plate holder (8) sits in a track marked with degrees around the perimeter of the spectrometer. Given the significance of the results, the photographs are very unassuming (9).


(1) Inv. Num. 94316 Newton Induction Coil [not original Moseley apparatus but representative]


(2) Inv. Num. 19106 Main X-Ray Tube and Trolley Bobbin Tube


(3) Inv. Num. 22996 Trolley Apparatus for Target Samples

(4) MS Museum 118 Small envelope containing 3 photographic prints of spectra and modern envelope and stiffener containing 5 similar photographic prints of spectra


(5) Inv. Num. 20275 Lead Collimator Slit


(6) Inv. Num. 17217 Spectrometer, by Charles W. Cook


(7) Inv. Num. 28094 Mounted Potassium Ferrocyanide Crystal


(8) Inv. Num. 15401 Photographic Plate Holder


(9) Inv. Num. 98186 Photograph (Gelatine Print) of X-Ray Spectral Lines

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