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Arc, sighting

Details

Artifact no.
1995.0671.001
Manufacturer
Unknown
Manufacturer Location
England
Manufactured Date
Between 1880 - 1910
Context Function
TO DETERMINE SLOPE OF MINE SHAFTS, WHEN USED WITH COMPASS OR CIRCUMFERENTOR-TYPE SURVEY INSTRUMENT
Context Technical
DEVICE DESIGNED SPECIFICALLY FOR MINE SURVEYING, AS EVIDENCED BY SCALE. ARC WOULD BE MOUNTED ON A COMPASS OR CIRCUMFERENTOR FITTED WITH BUBBLE LEVELS. THE ARC WOULD HAVE BEEN SIGHTED UP OR DOWN A MINE SHAFT & THE COMPASS LEVELLED WITH THE BUBBLES. THE READING THEN PROVIDED THE GRADE, IN FEETIN A FATHOM (6 FT) (PER RCB)
Context Canada
NONE SPECIFICALLY. INSTRUMENTS SUCH AS THIS COULD HAVE BEEN USED IN CANADIAN MINES.
Description
BRASS CONSTRUCTION, SAVE ARC SCALE FACE & READING INDICATOR WHICH ARE PROBABLY DIVIDED ON SILVER
Number of Parts
1
Artifact Finish
ALL SURFACES SAVE FACE OF SCALE HAVE OXIDIZED BRASS FINISH. SCALE FACE HAS THIN LACQUERED FINISH APPLIED. CENTRAL PIVOT FITTING & ATTACHMENT SCREWS ALL HAVE LACQUERED BRASS FINISH
Artifact Markings
ARC DIVIDED +5-0-5+ FEET BY 1-INCH INCREMENTS ON INNER EDGE; OUTER EDGE DIVIDED +1-6-1+ FEET BY 1-INCH INCREMENTS. INNER SCALE LABELLED 'Perpr' AT EITHER END; 'FOOT' INCISED ON EITHER SIDE OF '0'. OUTER SCALE LABELLED 'FOOT' ON EITHER END; 'Underlie in a Fathom' INCISED IN CENTRAL PORTION OF ARC.
Artifact Missing
SCREW FITTING LEFT SIGHT TO ARC NOT ORIGINAL. CROSSHAIRS IN BOTH SIGHTS BROKEN BUT PRESENT. LEFT SIGHT VANE MAY ALSO BE REPLACEMENT, AS IT IS DIFFERENTLY CONFIGURED AT ATTACHMENT POINT, DESIGN RE: FOLDING MOVEMENT *
Group 1
Exploration and Survey
Category 1
Measurement-angles
Subcategory 1
Horizontal
Material
metal->brass;metal->silver
Length
19.0 cm
Width
19.0 cm