overall: 1 in x 2 3/4 in x 2 3/4 in; 2.54 cm x 6.985 cm x 6.985 cm
overall: 1 1/4 in x 2 3/4 in x 3 1/8 in; 3.175 cm x 6.985 cm x 7.9375 cm
United States: Colorado, Denver
The Brunton Pocket Transit was said to be "the most convenient, compact and accurate pocket instrument made for preliminary surveying on the surface or underground." It has a folding sight at north. The lid of the instrument, hinged at south and provided with sight line and small hole, serves as the second sight. Since the lid is mirrored, the user can read the needle while sighting a distant object. The needle ring is graduated to degrees. The western half of the face is graduated in degrees, in quadrants from west, and provided with a clinometer with vernier that reads to 5 minutes. The sides of the case and lid are flat, and so the instrument can be set up vertically when used for vertical angles. This example is marked "D. W. BRUNTON'S PAT. SEPT. 18, 1894 APR. 14, 1914 WM. AINSWORTH & SONS SOLE MANUFACTURERS PAT. OCT. 2, 12. MAY 27. 13. DENVER, COLO. U. S. A. 14711." It was owned by the University of Missouri at Columbia, and was probably made between 1915 and 1919.
David W. Brunton (died 1927), a Canadian–born surveyor working in Colorado, invented this instrument after growing tired of carrying heavy equipment through the Rocky Mountains. He obtained his first patent (#526,021) in 1894, and subsequent patents in 1912 (#1,042,079), 1913 (#1,062,582), and 1914 (#1,092,822). The Wm. Ainsworth Co. of Denver began marketing these instruments in 1896, and by 1899 had sold more than 200 units. The firm became Wm. Ainsworth & Sons in 1905. The Brunton pocket transit remains in production today in Riverton, Wyoming.
Ref: Wm. Ainsworth & Sons, <i>Catalog BX of Precision Engineering and Surveying Instruments</i> (Colorado, 1908), p. 62.
Peter von Gitter, "The Brunton Pocket Transit, A One Hundred Year Old North American Invention," <i>Earth Sciences History</i> 14 (1995): 98–102.
Currently not on view
Wm. Ainsworth & Sons. Catalog BX of Precision Engineering and Surveying Instruments
History of Earch Sciences Society. Earth Sciences History
University of Missouri-Columbia, Department of Civil Engineering