Like the prismatic compass for which Charles Schmalcalder obtained a British patent in 1812, this one lets the user read the card while sighting a distant object. It has a tall folding sight at north, and at south, a shorter sight with a prismatic eyepiece at its base. The floating card is bright green; the numbers around its edge read correctly when seen through the prismatic eyepiece. Unlike the Schmalcalder instrument, this one has a solid plate covering most of the card. It was termed an Improved Hutchinson Prismatic Compass, said to be lighter and less bulky "than the old form," and was "adopted by the various branches of the English and Foreign Services." This example, which belonged to the University of Missouri at Columbia, is marked "A. S. ALOE CO. ST. LOUIS." A. S. Aloe & Company became A. S. Aloe Co. in 1894.
Ref: James J. Hicks, Illustrated & Descriptive Catalogue (London, 1876), p. 141.
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