Reference numberMS/119/2/112
TitleLetter from Samuel Owen Edgar Ludlow, Madras [Chennai] to Humphrey Lloyd, Trinity College, Dublin
Date24 November 1841
DescriptionLudlow informs Llyod that he received his letter and is making changes Lloyd recommended at the Madras Observatory. Ludlow informs Lloyd that he has changed the position of the vertical force pillar and will continue to observe the needle in its new position. Discussion regarding the large wheels of the horizontal force instrument. Ludlow has been reading the magnetic and meteorological instruments hourly, and for the last few months the magnetic instruments every half hour, Ludlow is now reading them every 15 minutes to determine more accurately the movements of maximum and minimum.

Ludlow has made a small pavilion made with a stone pillar at a distance from the observatory, for the purpose of experiments of vibration which are made simultaneously during horizontal force observations. A small room has also been constructed which houses the declination magnetometer and allows Ludlow to make more frequent observations. Ludlow discusses his regular series of observations of the horizontal intensity. Ludlow asks Lloyd’s the shortest distance the magnet should be placed. The magnets at Madras Observatory are 15 meters long, Ludlow describes the present positions with distances, and the results he obtains.

Ludlow is troubled by the different dip results he has obtained with different needles.

Ludlow will soon receive a new circle provided with four needles, made by the late [Thomas Charles] Robinson.

Ludlow discusses the trouble he is having with the suspension threat of the declination magnetometer. When the magnet has been taken out and replaced there is a noticeable difference even though no change has occurred. Ludlow argues this is due to the axle not occupying the same position, and includes a small diagram demonstrating his point.

Discussion on the changes and arrangements Ludlow has made to the instruments.

Ludlow asks Lloyd if he thinks Sir [John] Herschel would like to know the contents of this letter, and if so would Lloyd be able to forward this letter to Herschel.
Physical descriptionInk on paper.

The letter has two holes where presumably the wax seal has been broken.
Access statusOpen
Fellows associated with this archive
NA8252Lloyd; Humphrey (1800 - 1881)1800 - 1881
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