Hackman stereo slope comparator
Date: circa 1960
Inventory Number: 1996-1-0529
Classification: Stereo Slope Comparator
Subject:
Maker: The A. Lietz Company (1882 - ca 1980)
User: Department of Geology and Geography, Harvard University (1890 - 1961)
Cultural Region:
Place of Origin:
Dimensions:
comparator: 5 × 23 × 9.5 cm (1 15/16 × 9 1/16 × 3 3/4 in.)
case: 8.5 x 31 x 13 cm (3 3/8 x 12 3/16 x 5 1/8 in.)
Description:
This instrument was meant to be put on topographic maps. (There is felt under the comparator to provide stability and to keep the maps undamaged.) The upper knob is used to extend the width between the two yellow perforated attachments pieces, fixed at the end of the comparator's arms. These attachments are secured in place by a small rod a thumb screw. The front knobs on the side rotate the attachments sideways (called the strike of the slope); the back knob moves the attachments up and down (called the dip of the slope). The latter is measured on a semi-circular quadrant marked 0-90°-0 and divided in single degrees.
The instrument is stored in a wooden case lined with felt when not in use. The inside lid has a compartment with a sliding cover to store the four differently shaped pairs of perforated yellow attachments.
The instrument is stored in a wooden case lined with felt when not in use. The inside lid has a compartment with a sliding cover to store the four differently shaped pairs of perforated yellow attachments.
Signedon comparator and box lid plaque: LIETZ
FunctionFor measuring the strikes and dips (or the topography) of geologic formations in aerial photographs. This model was designed by Robert J. Hackman.
ProvenanceFrom the Department of Geology and Geography, Harvard University.