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Description: | 20-0-20 (degree scales engraved on two brass one ninth arc bezels at either end of the case.). J Jackson (engraved on the south bezel). L.Ma.12a. (in aluminium paint on the glass, removed) MANU JACKSON,Joseph. scond half 18th century London, England. DES after GRAHAM,George. 1722 London, England. This variation compass or declinometer in a long brass case with a needle support which appears to be a machined piece of clear mineral ?quartz, diamond, or sapphire was used to determine the very small angles of magnetic variation caused by solar flares. The phenomenon of magnetic variation was reputedly first demonstrated to the king of Siam by Father Tachart in 1682. George Graham noticed small variations in declination in 1722 using his own design of sensitive compass. Anders Celsius (1701-1744) visited Graham in 1735 and obtained from him an instrument made by Jonathan Sisson. When he returned to Uppsala in 1737he began hourly observations and published these in the 1740 Proc.Roy. Soc. Acad. Sci. After the death of Celsius his assistant Olof Hiorter continued the research. The connection between the aurora borealis and was made independently by Celsius and Hiorter in April 1741 during an episode of particularily violent solar activity. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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