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THE BRUNTON POCKET TRANSIT,
A ONE HUNDRED YEAR OLD
NORTH AMERICAN INVENTION

 

Peter H. von Bitter PhD.

Curator, Department of Invertebrate Paleantology
Royal Ontario Museum and Professor, Department of Geology,
University of Toronto, Toronto, Ontario M5S 2C6, Canada

 

Made in United States of America
This article was printed in the journal of the History of the Earth Sciences Society, Earth Sciences History
Vol. 14, No. 1, 1995
Copyright 1995 by HESS

HTML and additional notations by William James Hudson

On September 18, 1994, Brunton's Patent Pocket Mine Transit, and its descendants, completed one hundred years of distinguished geological service. David William Brunton, Mine Manager and Mining Engineer, of Aspen, Colorado, was awarded Patent No. 526,021 by the United States Patent Office on September 18, 1894 1,2 for the instrument (Figures 1,2) known to generations of geologists as simply "the Brunton".

Figure 1Figure 2

Figure 3 - David W. Brunton

David Brunton (Figure 3) was born at Ayr, Ontario, Canada on June 11, 1849, the fourth oldest son of James and Agnes Brunton. The Bruntons were an old Scottish border family and James Brunton was born in Galashiels, Scotland in 1819; he died in Mount Pleasant , Ontario, in 1865. David Brunton's mother, the daughter of John and Jane Dickie, was born at Kilmarnock, Scotland in 18245-8. After receiving his education in Toronto5, David Brunton followed his father's footsteps6 and began an engineering apprenticeship in 1870, initially under Edmund Wragge, Chief Engineer of the Toronto, Grey and Bruce Railway and subsequently, in 1871, under J. C. Bailey, Chief Engineer of the Toronto and Nipissing Railway1. During 1874-1875 Brunton took a "special course" in chemistry, metallurgy and geology at the University of Michigan at Ann Arbor1,9 and, in June 1875, he left Michigan for Colorado to begin a highly successful career as mine manager, mining engineer, entrepreneur, inventor and consultant1,5,9. Brunton married Katherine Kemble of Kingston, New York on February 11, 1885; they had four children - Frederik K., John D., Harold J., and Marion1,5,8.

Early in his career Brunton became frustrated by the number of instruments that a mining engineer had to carry in order to conduct surveys. Consequently, he undertook to design a universal instrument that he could carry in his vest pocket. After making a half-dozen prototypes1, each an improvement over its predecessor, he attained the design which was patented. In the early years, the exclusive maker of the Brunton Pocket Transit was the Colorado instrument maker, Wm. Ainsworth11 (after about 1898, Wm. Ainsworth & Sons3) initially of Central City, later of Denver. By July 1899 about 200 of the Brunton Pocket Transit instruments were in daily use3; by 1929, this number was claimed to be 30,00012; 30 years later, it had reached 60,00013.

Despite the close adherence by Wm. Ainsworth & Sons to the original specifications of weight (8 oz. or less)2 and size ( 2 3/4" X 2 3/4" x 1" )2, the Brunton Pocket Transit did not remain static and a number of improvements were made by Brunton over the years. Patent no. 1,042,079 dated October 22, 19121 added a second bubble tube at right angles to the first (Figure 4), a single-holed peep sight on the cover, improvements to the sighting arms, and the modifications necessary for attaching the pocket transit to a telescopic tripod. Patent no. 1,062,582,  dated May 27, 1913, sought to improve the sights of the pocket transit to fully utilize the attributes of the 1912 patent and to permit backsighting in areas where local magnetism would affect the accuracy of the needle 1. Geological users' criticism of too restricted a field of view was met by patent no. 1.092,822 dated April 14, 1914 in which larger apertures, formed by two overlapping circular openings on the two peep sights, were provided. The 1914 patent reduced the number of bubble tubes back to one1; it is not known if a two-bubble tube version of the pocket transit was ever produced. [EdNote 1]  It also remains uncertain precisely when Brunton added the now standard bullseye level. It was not shown on patent no. 1,339,019 dated May 4, 1920 1 (see next paragraph), but was illustrated and termed "the round level" in 192912; a July 20, 1926 patent recorded on the lid of Brunton Pocket Transit no. 18101 (Figures 5, 6) may have dealt with this modification. [EdNote 2]  A universal alidade14 , designed to fit over the glass cover and to be used for taking steep sights, was described as new in 1929 (Figure 7).

Figure 4 - Drawing from 1912 patent 

Figure 5 - Brunton Pocket Transit 18101 Figure 6 - Brunton Pocket Transit 18101Figure 7 - The Universal Alidade, A Brunton Compass Accessory

David Brunton was very involved in the American war effort during World War I1 and, among other things, he adapted his pocket transit for military use. Patent no. 1,339,019 dated May 4, 1920 was for an "Illuminated Transit", for day or night use, in which the 'night circle', cut into the under side of the cover glass, was illuminated by luminous radium paint. The caption for the patent documentation reads "Night view of instrument with MARVELITE illuminated cover glass, needle and sights for military use."1 The writer does not know if the radium-bearing military version of the pocket transit ever reached the production stage. Wm. Ainsworth & Sons are known to have produced variant models of the pocket transit; one, graduated in mils, was designed for fire control of nonportable machine guns during World War I, and another, the M-2 compass, again graduated in mils, was used for field artillery fire control during World War II15. Of interest is the fact that The Brunton Co. still manufactures and sells the M-2 version of the pocket transit for military purposes16,17. David Brunton also developed a graduated celluloid alidade to be used with the pocket transit "for filling in details [in mapping] from established control points."1 The military ordered 14,800 of these1 and a modified version, presumably for peace-time purposes was marketed by Wm. Ainsworth & Sons in 192912.

Possibly as early as 1911 (when Brunton's original patent protection would have expired18, but certainly by 1913 (when Keuffel and Esser Co. advertised a pocket trasit that was practically a clone of the one invented by David Brunton, as "after Brunton"19), there must have been severe competition from manufacturers of virtually identical instruments. British, German and Japanese companies have produced, and are still producing Brunton-style transits very similar to those formerly made by Wm. Ainsworth & Sons. The most noteworthy of these seen by the writer is a well-made model by Ryland and Son Ltd. of London; this instrument closely follows the Ainsworth design, but is completely made of brass rather than the normal aluminum and weighs an astonishing 1.5 pounds. [EdNote 3]

Although Wm. Ainsworth & Sons ceased to manufacture surveying transits about 1940, when that part of the business was sold20 the company continued to make Brunton Pocket Transits through the 1950s13 and 1960s21. It was during the latter period that Ainsworth introduced a new feature - induction damping - that allowed the quivering compass needle to come to rest faster22.

The rights to manufacture the Brunton Pocket Transit and to the Brunton name were acquired by The Brunton Co. in 197217. This company, with headquarters in Riverton, Wyoming, has, in the intervening years, added new features to the pocket transit including digital readout (1975), waterproofing (1976), and a composite body with waterproofing (1985). A gold-plated presentation model was offered a number of years ago and a glass-filled composite waterproof Brunton has become a best-seller in recent years17.

David William Brunton died in Rochester, Minnesota, December 206 or 217, 1927; the consummate inventor, he would, no doubt, be pleased with the advances made and would probably wonder how the next century will change and improve his still widely-used pocket transit.

 

ACKNOWLEDGEMENTS

I thank John M. Shannon, Lakewood, Colorado and Kay D. Wisnia, Denver Public Library, Western History Department, for their kind and generous help; without their assistance this article could not have been written. I also thank Dale Beeks, Cour d'Alene, Idaho, John Cox, The Brunton Co., Riverton, Wyoming William J. Daniels, Toronto, and Robert C. Miller, New Alexandria, Ohio, for helpful discussion and information. It is a pleasure to acknowledge the help of David W. Brunton of Montrose, Colorado, in providing information about his grandfather. Finally, I am indebted to Joan Burke, Champa Ramjass, Brian Boyl and Ron Pozniak, Royal Ontario Museum, Toronto, for exercising their skills so professionally.

 

NOTES

  1. Brunton, D. W., ?1920. Engineering record, 1870-1920, typed manuscript diary, 2 vols. (includes drawings, photographs and diagrams, etc. of Brunton's numerous inventions). 184 p. Denver Public Library, Western ?History Division, call no. C MSS WH5 1 M34-540
  2. Mines and Minerals, February 1899, p. 320: detailed description of the use and advantages of "Brunton's Patent Pocket Mine Transit".
  3. Mines and Minerals, July 1899, p. 73;advertisement for "Brunton's Patent Pocket Mine Transit" by Wm. Ainsworth & Sons.
  4. Geotimes, May-June 1964, p. 40; advertisement for Brunton Pocket Transit by Wm. Ainsworth & Sons, Inc.
  5. W. C. Ferril, 1911. Sketches of Colorado vol. 1. The western Press Bureau Co. 419 pp. Denver Public Library, Western History Division, call no. 978.8.
  6. T. A. Rickard, Obituary of David W. Brunton; newspaper clipping - source and date unknown - supplied by The Brunton Co.
  7. Denver Public Library, Western History Division; computer entry for Source #1.
  8. Newspaper clipping - source and date unknown - entitled "Dave Brunton Credits Young Men with his Success"; supplied by The Brunton Co.
  9. D. W. Brunton, 1915, Technical Reminiscences. In Mining and Scientific Press, November 27, 1915, pp. 3-20; Denver Public Library call no. C622.09 B834+.
  10. J. G. Canfield, Publisher, 1893, Mines and mining men of Colorado, historical, descriptive and pictorial. 188 pp. with illustrations, Denver. Denver Public Library call no. 978.86 C162 mi.
  11. Mines and Minerals, July, 1898, p. 72; advertisement for "Brunton's Patent Pocket Mine Transit" by Wm. Ainsworth.
  12. Wm Ainsworth & Sons, 1929 Instruction booklet for the use of "The Improved Brunton Patent Pocket Transit".
  13. Geotimes, May-June 1959, p. 29; advertisement for the Brunton Pocket Transit by Wm. Ainsowrth & Sons, Inc.
  14. S. A. Ionides, no date, but 1929 or earlier. Instruction booklet for the use of "The Universal Alidade, a new Brunton Accessory (Patent Applied For)" manufactured and distributed by Wm. Ainsworth & Sons, Inc., Denver, Colorado.
  15. Ainsworth family - personal communication between Robert Ainsworth and John Shannon.
  16. A Bit of History; The Brunton Co., August 1984. Supplied by The Brunton Co.
  17. John Cox, The Brunton Co. (personal communication, 1994).
  18. Robert C. Miller, New Alexandria, Ohio (personal communication, 1994).
  19. 1913 Catalogue of Keuffel & Esser Co., Manufacturers and Importers, Drawing Materials, Surveying Instruments, Measuring Tapes. 566 p. Canada Edition, New York.
  20. John Shannon, Lakewood, Colorado (personal communication, 1994).
  21. Geotimes, July-August, 1964, P. 21; advertisement for Brunton Pocket Transit by Wm. Ainsworth & Sons, Inc.
  22. Geotimes, July-August, 1967, p. 27; advertisement for Brunton Pocket Transit by Wm. Ainsworth & Sons, Inc.

The writer would be interested in hearing from anyone with information on David Brunton, on the evolution of the Brunton Pocket Transit, or from those having early Brunton Pocket Transits.
 

Editor's Notes:

  1. It is now known that two-bubble tube versions were in fact produced. However most are not exactly as pictured in the patent, instead  having the second tube set to the right of the first tube.
  2. Brunton Pocket Transit no. 17393 which also has the July 20, 1926 date was manufactured with the crossed long levels instead of the bubble level.  I have recently been able to locate the 1926 patent, number 1,593,429, which details the  addition of the percent grade scale to the clinometer.
  3. Dr. von Bitter wishes readers to know that he now believes that the brass version he viewed was most likely a late modern copy manufactured in India or Pakistan. The more recent flood of brass copies on the market are of much poorer overall quality.

Peter H. von Bitter, "The Brunton Pocket Transit, A One Hundred Year Old North American Invention," Earth Sciences History, 1995, 14:98-102

Permission to reprint this article on this website was granted by Dr. Gregory A. Good, Editor of Earth Sciences History on February 9, 2004. This article may not be reproduced in any form without the express written consent of the History of Earth Sciences Society.