Abstract
DURING the last vacation St. John's College, Oxford, has been lit with the electric light, and a transformer of the dynamomotor type, weighing over seven tons, has been placed within about sixty feet of the electrical testing room of the Millard Laboratory, which is furnished with several reflecting galvanometers. I greatly feared that the instruments would suffer much from the magnetic field of the large transformer. When it was found that no other space could be given up for the machine, I devised a method of construction which the Oxford Electric Lighting Company very kindly carried out for me when building their dynamo house. My method is to construct a wall of scrap iron round the three sides of the dynamo nearest to our laboratory. The iron wall is about eight inches thick, and is made by building two brick walls parallel to one another, and filling the interspace with scrap-iron; a delicate magnetometer used for testing the field at unprotected and protected points equidistant from the magnets, when the machine is in action and not so, shows that the iron wall is an effective barrier to the magnetic influence. I venture to make known this method of shielding off a magnetic field, because in these days of electrical invasion it may be of use in protecting physical instruments from being seriously disturbed, and rendered useless for any but the roughest determinations.
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SMITH, F. A Magnetic Screen. Nature 47, 439 (1893). https://doi.org/10.1038/047439d0
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DOI: https://doi.org/10.1038/047439d0
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