File:Astronomical discovery (1904) (14800175633).jpg

Identifier: cu31924012301655 (find matches)
Title: Astronomical discovery
Year: 1904 (1900s)
Authors: Turner, H. H. (Herbert Hall), 1861-1930
Subjects: Astronomy
Publisher: London, E. Arnold
Contributing Library: Cornell University Library
Digitizing Sponsor: MSN

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nelastic needle so as to make a mark on a sheet ofpaper, and if for a moment we exclude the upand down movements, the pencil would describeduring the day a curve on the paper, as the endof the needle swung backwards and forwards withthe change in direction, and moved across thedirection of swing with the change in intensity.Now when curves of this kind are described for aday in each month of the year, there is a strikingdifference between the forms of them. DuringDifference the summer months they are, generally speaking,summer Comparatively large and open, and during theand win- winter mouths they are small and close. Thischange in form is seen by a glance at Plate XIII.,which gives the curves throughout the whole ofone year. Let us now, instead of forming a curveof this kind for each month, form a single averagecurve for the whole year; and let us further dothis for a series of years. (Plate XIV.) Wesee that the curves change from year to year in a GREENWICH MAGNETIC CURVES 1859-60 I
Text Appearing After Image:
Plate XIII. SAt^ I fpAt

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