Reference numberMS/119/2/59
TitleLetter from Charles James Buchanan Riddell, Woolwich to Humphrey Lloyd
Date13 March 1845
Description[Edward] Sabine informed Riddell that Lloyd wrote to him in answer to [John] Herschel’s circular, and Lloyd intends to write about the vertical force magnetometer in the northern expedition. Riddell suggests alterations to the vertical force magnetometer. Riddell notes that the magnetometer will be the same in all other regards to the Toronto magnetometer, but will be fitted with a mirror instead of the micrometer wires. Riddell argues the benefits of adopting the mirror. Riddell called to see the vertical force instrument at Greenwich observatory, which is fitted with a mirror only, and describes the instrument. [Henry] Barrow called Riddell and does not see any difficulty in fixing the mirror accurately perpendicular to the magnetic axis. Discussion on the direction of the magnets when adjusted and comparisons made with the Greenwich observatory instrument.

Discussion on the induction inclinometer. Riddell describes changes to the instrument to manage the large changes of declination. Riddell sends Lloyd a memo that notes one quiet bar will be enough [not enclosed].
Physical descriptionInk on paper
Access statusOpen
Fellows associated with this archive
NA7327Riddell; Charles James Buchanan (1817 - 1903)1817 - 1903
NA8252Lloyd; Humphrey (1800 - 1881)1800 - 1881
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