Description:
- Object ID: ALSA 2012.02.02
- Made by: Keuffel & Esser Co.
- Model: Unknown.
- Serial Number: 103971
- Date Made: Unknown.
- Approximate size: Bottom Plate: 29 X 8.5 cm. Telescope: 25 X 4 cm diameter.
- Accessories: wooden case.
- Condition: Good
Commentary:
Attached to the plate of the alidade is a trough compass in a wooden case. Graduated scales are on both sides of the plate. “KEUFFEL & ESSER CO.” and Serial No. “103971” is engraved on the top of the plate. A striding level is attached to vernier connected to the telescope.
The telescope has stadia lines so it can be used for determining distances by stadia (see below). The alidade also had a vertical circle so that the slope of the measurement could be determined for reducing slope distances to the horizontal and also to determine differences in elevation.
There is a Keuffel & Esser label inside box showing “no 5095A” which is assumed to be the model number and “serial 10391.” It also shows the stadia fixed ratio as 1:100. The distance from the instrument to a stadia rod is determined by subtracting the bottom stadia line reading from the top stadia line reading on the rod and multiplying the difference by the stadia fixed ratio which in this case is 100.
Lou Breton who donated this object also donated a plane table and tripod (ALSA 2012.02.01) and a trough compass (ALSA 2013.01.02).
Source of Object: Donated by Lou Breton, ALS (Hon. Life).
Notes: The Society has two other Alidades of this type in its collection: a W. & L.E. Gurley (ALSA 2007.05.01) and a Bausch & Lomb (ALSA 2010.06.07).
References: Visit article The Survey Instrument Captain Cook Wanted to Learn – The Plane Table and Alidade for additional information.
Description by: Entered by Ed Titanich on December 23, 2024.