David W. Bunton and his compass
August 4, 2010
Aspen, on the leading edge of mining, attracted the best in the profession. As mining engineer David W. Brunton dominated mining circles in the 1890s and early 1900s, he established a residence and business in Aspen. Brunton’s patented innovations for mining machinery were accepted worldwide.
Brunton ran a 600 ton per day sampling works in Aspen. His partner F.M.Taylor and W.S. Copeland, his nephew and manager, joined him in purchasing ore from local mines. They used Brunton’s patented process to sample and accurately mix ore before selling and shipping it to smelters. A sampler measures an exact quantity of material passing through the device; 1/25th of that amount is then assayed for mineral content, ascribing a value for the entire quantity. Brunton and Taylor operated similar samplers in Cripple Creek and Salt Lake City.
Brunton wrote a book on mine tunneling, was a consultant to Anaconda Mining Company, and served as an advisor to the U.S. Navy in World War I. In addition, he invented a mining pump, an electric hoist, a mine car coupling, and a system of round timber framing.
David Brunton is more widely known for inventing a specialized compass that still bears his name. The Brunton Pocket Transit is familiar to field engineers, anthropologists, archeologists, geologists and military commanders – anyone who needs to perform quick and accurate surveys.
That compass, patented in 1894, was widely used in underground mines. Surveying a tunnel, as well as locating claim corners on the surface, becomes a time-consuming, complicated procedure. The Brunton compass can be clipped to your belt or carried in a large pocket. With its clever mirror, it can be attached to a tripod and plum bob, replacing a costly and unwieldy surveyor’s transit, while producing fairly accurate surveys. The instrument also has a built-in level that allows users to measure the vertical angles that are so informative to geologists and miners as they map the strike and dip of geologic layers and ore veins. Surveys of many Aspen mines were accomplished using solely a Brunton compass, as was the first survey of Aspen’s lift lines in the 1940s.
Brunton, a Canadian immigrant, opened an engineering office in Denver and split his time among his enterprises. After patenting his compass he hired William Ainsworth, a skilled watch repairman in Central City, to manufacture his compasses. To date, more than 150,000 Brunton Pocket Transits have been manufactured.
You can still buy a Brunton compass, manufactured by the Brunton Company, even through Amazon.com. Some materials have been substituted, and a few improvements have been made, but the modern version resembles the originals. Apparently they retain their original utility, because they are seldom to never found in local antique shops.
Brunton’s home in Aspen has also survived. Look for it among the two-story Victorians on the north side of Main Street, between 3rd and 4th streets. The house concretely manifests the enduring legacy of one of Aspen’s mining-era celebrities.