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North.
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Photographs of Spiral Nebulæ. By Dr. Max Wolf.
1. Great Nebula in Andromeda. 2. Spiral in Triangulum (M. 33).
Another remarkable example of a spiral nebula will be found in M. 51. It is situated in the constellation Canes Venatici, and may be easily picked up, being not far from the end star of the Plough-handle Eta Ursæ Majoris. This strange object, 'gyre on gyre' of fire-mist, was one of the first spirals to have its true character demonstrated by the Rosse telescope. It is visible with moderate optical powers, but displays to them none of that marvellous structure which the great 6-foot mirror revealed for the first time, and which has been amply confirmed by subsequent photographic evidence (Plate [XXXII.]).
Photograph of Whirlpool Nebula (M. 51). Taken by Mr. W. E. Wilson, March 6, 1897.