Surveying Instrument Collection
Maker |
N/A |
Model |
Sirius |
Serial Number |
53244 |
Dimensions |
Diameter 100mm |
Image |
|
Description |
This instrument is a form of Prismatic compass known as the Liquid compass, and is so-called since the needle and it's accompanying graduated disc float in a special fluid contained in the case. The object of this arrangement is to reduce wear of the pivot and of the bearing of the needle. It also assists in damping down the needle's oscillations. The prismatic attachment consists of a 45 degree reflecting prism with the eye and reading face made slightly convex so as to magnify the image of the graduations. Most of these liquid compasses can have their dials painted with radium compound to enable readings to be taken at night, without the necessity of other illumination - an obvious advantage for military purposes. The instrument features a female thread underneath, for attachment to a lightweight tripod. The floating disk carries the inscription 'Esdaile'. |
History & comments |
The liquid in the compass can be a great advantage, but is of course rather more expensive than the usual form. It's main advantages are that it is rather more sensitive owing to the reduced weight on the pivot, and that, as it is practically dead beat, the readings may be taken in much less time. On the downside however, as the image above shows, air bubbles may may appear in the liquid over time, making the device unstable. |
Conservation |
In a container |
Condition |
Good condition |
Remarks |
|
Dates |
Manufactured in 1900 (approx). Catalogued in 1997 & 2005 |