Reference numberMS/119/2/104
TitleFirst half of letter from Joseph Henry Kay, Magnetic Observatory Rossbank to Humphrey Lloyd
Date2 March 1842
DescriptionKay informs Lloyd he has put Lloyd's suggestions into operation, but notes that the distance between them causes difficulties in communication. Kay answers Lloyd's questions and concerns regarding the work at the Rossbank observatory Van Diemen's Land [Tasmania; Lutruwita or Truwana], and replies to his letter from 6th May. Discussion on the horizontal force magnet, and Kay addresses the error in the first estimation of the angle . The torsion circle with the plane of detorsion was correctly found by Captain James Clark Ross. Kay then substituted a roller and found the diurnal suspension of the changes of horizontal intensity to be greater.

Discussion on the declination magnetometer. Kay describes experiment of attaching a bar to the suspension thread at certain times over the course of 14 months. Kay suggests using tangent screws to the torsion circle in any instrument to be constructed, this would greatly facilitate the adjustments.

Kay informs Lloyd that the reading telescopes have been shifted for the first time since they were installed in October 1840. Kay has sent Lloyd the previous angle but has not yet determined the new angle.

Kay has adopted Lloyd's method of determining the magnetic axis of the declination bar by alternate readings in the direct and reversed positions, rather than Ross's method of taking a number of consecutive readings first one way and then the other. Kay asks Lloyd wether his method of determining the axis after the sliders have been removed is correct, as he finds it impossible to put the sliders back in precisely the exact same position because the slightest turn of the screws alters the position of the scale.

Kay has changed the position of the vertical force magnet, and it is now at right angles to the meridian. Kay has written to Ross at the [Falkland Islands] regarding this matter, Ross was of the opinion to keep the vertical force magnet in the plane of magnetic meridian. Ross has made all his observations with this position, and Kay fears that in their small portable observatories the mutual action will be more considerable in comparison to the Rossbank observatory. Kay describes the way he overcame his principal difficulty in diminishing the extreme sensibility of the instrument. Kay has recently performed the vibrations in the vertical plane once a week and monthly in the horizontal plane. Kay is satisfied that the vertical force instrument is now doing well and not deficient in sensibility.

Kay addresses Lloyd's view that the deflection distance at Rossbank observatory is too great.

Discussion on the method of ascertaining absolute intensity.

Kay states his intentions to commence a series of observations with the inclination instrument.

The changes in the building for reducing the the internal variation of its temperature have not been effected. Kay notes that due to the daily arrival of prisoners the engineers department have been unable to deal with this matter.

Kay informs Lloyd that he has not received the copper rings, which would save him a lot of trouble when checking the arcs of vibration.

Kay addresses Lloyd's disapproval of two places of decimals in the result of a single observation, and explains his reason for this.

Kay informs Lloyd that he has recently received Lloyd's welcome letter ten months after it was sent to him, despite the passage from England being 90 days. Kay notes that had he received Lloyd's letter sooner he would have been in a position to correct Ross regarding the vertical force instrument, in which Ross is in error.

Kay assures Lloyd regarding his commitment to their work and endeavour and expresses his zeal coming from a higher motive.

Discussion on taking true readings at the extremities of the arc of vibrations on term days form the beggining. Kay's intends to vibrate the needle in the vertical plane weekly.

Kay describes changes he has made to the instruments at the Rossbank observatory. Kay intends to never lift the vertical force from its agates. The horizontal force will never be removed for the purpose of swinging it. Kay informs Lloyd that he sending information regarding the declination magnetometer and telescope, the constant angle and an approximate table of the declinations observed at Rossbank for 15 months [not enclosed]. Kay is intending to make alterations to the observatory to form an effective method of reducing the internal temperature. Includes a list of the horizontal force thermometers readings fort he last 12 months, and discusses the small range despite the variability of the climate.

[The second half of this letter is MS/119/2/105]
Physical descriptionInk on paper
Access statusOpen
Related records in the catalogueMS/119/2/105
Fellows associated with this archive
NA4898Kay; Joseph Henry (1814 - 1875)1814 - 1875
NA8252Lloyd; Humphrey (1800 - 1881)1800 - 1881
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