Author: GILL, David.- to J.A.H GYLDEN [Recipient] ALS.- Cape Observatory.- 1896
Title: Important autograph letter signed and dated 'Cape Observatory....1896 to [Johan August Hugo] Gylden, ...., in which David Gill asks for literature on Edvard Jâderin's base line measuring apparatus and asks Gyldén to put him into contact with him '.....' Letter written by the then Director [or Her Majesty's Astronomer at the Cape] David Gill. Autograph.
Description: Royal Observatory Cape of Good Hope, autograph, 1896. Dated: '1st January 1896'. 4to. [Meas. appr. 18.5 x 23 cm.]. On lightcol. letterhead Observatory paper, w. blind embossed stamp top center, single smaller sized sheet, 31 lines in autograph by David Gill, with his signature. David Gill was H.M. Astronomer at the Cape between 1879 - 1907, he was a meticulous observer and his important work includes solar parallax observations with a heliometer, the use of dry plate photography to capture position and brightness of over half a million southern stars [in colllaboration with the Dutch astronomer Kapteyn], McClean was also leading in the venture to map the entire sky the 'Carte du Ciel'project. He became president of the Royal Astronomical Society in 1909 [to 1911]. His publication 'History and description of the Royal Observatory, Cape of Good Hope' [London, HMO, 1913] presents details on most every staff member and their publications up to 1913. On Johan August Hugo Gyldén [1841 - November 1896], Finnish Swedish astronomer, who specialised in celestial mechanics. Became the head of the Stockholm observatory in 1871 and astronomer for the Royal Swedish Academy of Sciences. Edvard Jäderin [1852 - 1923] , was a swedish astronomer and geodesist, university professor at Uppsala from 1907, led the Swedish Russian 1898 (preliminary) expedition to Spitsbergen (Svalbard) and the swedish party of the same expedition from 1899 - 1902. Jäderin was best known for his geodetic measurements, the Jäderin apparatus invented in 1880 was a base line instrument for the measurements of the bases of triangulations, the instrument consisted of wires [copper and silver] with scales suspended under constant tension from special mounts. ... See: Anne S. Troelstra, Bibl. of Nat, Hist. Travel Narratives, p 463 for Wulff & Jäderin: Howgego, [2006], p. 694: Hentze.

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