Reference numberMS/119/2/83
TitleLetter from Frederick Marow Eardley-Wilmot, Cape of Good Hope Observatory to Humphrey Lloyd, Trinity College, Dublin
Date7 August 1841
DescriptionDiscussion on the proceedings at the Cape of Good Hope observatory and updates Lloyd about any difficulties or confusion. Eardley-Wilmot discusses his ‘stupidity’ regarding the value of X in the experiment of deflection and vibration. The vast difference between its value found with the deflecting bar, and the horizontal force magnetometer, Eardley-Wilmot realised he had measured in inches rather than feet.

Discussion on the absolute measurement. Eardley-Wilmot notes that with practice the vibration can be managed with accuracy, however he is unable to get the similar beyond the third place of decimals. Eardley-Wilmot discusses his method for observing the vibrations and asks Lloyd if this would be suitable to proceed with.

Eardley-Wilmot is not pleased with the dip results. Dip needle reading was taken twice in the meridian.

Eardley-Wilmot is keen to receive Lloyd’s corrections. Eardley-Wilmot is unable to see why the value of X is differing in the two methods he has conducted, as well as the results of [Karl Friedrich] Gauss’s total intensity.

Eardley-Wilmot includes dip needle readings taken from Mr [Perry Professor of Match, United States Navy], from the Cape of Good Hope, Buenos Aires, Rio Steamboat Hotel Garden, and Montevideo.

There has been a slight shift in the position of the reading telescope of the declination magnetometer. Eardley-Wilmot suggests after the nuts were set in plaster of Paris they were painted which caused this shift, however he will alter the position as soon as he is able. Discussion on the effect of the copper apparatus when the bar without it has been perfectly at rest.

Eardley-Wilmot informs Lloyd that his underground house is nearly complete, and he will now be able to effect the absolute measurement without interrupting the declination magnetometer. Discussion on vibrations.

The anemometer does not act well, and Eardley-Wilmot will be taking it down, and raising a platform in its place. [Edward] Sabine mentioned that a new apparatus for the anemometer was soon on its way. The vertical force magnetometer appears to be regular it its indications, and Eardley-Wilmot observes its vibrations in the vertical plane every other day.

Eardley-Wilmot informs Lloyd that one of his officers got drunk, therefore had to be brought to a court martial. Eardley-Wilmot notes he was a very intelligent and useful man.

Since writing the above, Sabine has sent various packages, in the Adelaide transport, with the Company of Artillery for Cape of Good Hope station. Eardley-Wilmot includes diagrams of the underground house he has constructed, a section of the anemometer tower, the clock on the level of wheel, with dimensions.
Physical descriptionInk on paper
Access statusOpen
Fellows associated with this archive
NA6061Eardley-Wilmot; Frederick Marow (1812 - 1877)1812 - 1877
NA8252Lloyd; Humphrey (1800 - 1881)1800 - 1881
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