2010-04-10 / Columnists

Like Geocachers, Fur Traders Would ‘Cache’ Their Goods

A Look at History

Mackinac Island is scheduled to welcome a gathering of geocachers later this month. A call has gone out to enthusiasts to come to Mackinac Island and meet up in the lobby of Grand Hotel at 10:30 a.m. Saturday, April 24. The organizers, Michigan Geocaching, have posted a Web site that promises that participants will have the chance to look for about 70 caches hidden throughout the Island.

Most things rest on foundations that are below them. Geocaching is an adventurous sport that rests on some things that are far above us – namely the 24 busy global positioning system (GPS) satellites that orbit the earth, neatly placed in mathematical locations where they are always in a predictable location in space. With handheld devices, typically a handheld GPS machine or one of the current generation of GPS-enabled cell phones, geocachers hunt for precise locations. The geocache “treasure” will be hidden there. There are said to be more than one million geocaches hidden all over the earth today.

Our Mackinac Island furtrading forefathers would have understood the appeal of tracking in the spring woods. The word “cache” itself comes from the French language that many of them spoke; the word “cacher” means “to hide.” Fur traders and early explorers often “cached” their goods; for example, when Lewis and Clark were hiring men in and around Mackinac Island’s great rival, St. Louis, in 1803, they hired many trained fur traders who spoke French. Two years later in 1805, pushing up the Missouri River into what is now western Montana, these men saw the Rocky Mountains rising in front of them. They knew they would be coming back, so they carefully memorized certain sections of the riverbank, dug at least two separate holes, deposited some of the goods that they did not want to portage over the mountains, and called the holes “caches.”

In 1806 the successful explorers, who had reached and wintered on the Pacific coast, recrossed the mountains and retrieved their hoards. Lewis was sad, however, he admitted to his journal, that at least one of the caches, containing valuable bearskins, had gotten wet and the furs were ruined. Later fur traders learned how to dig and line relatively waterproof caches, searching for patches of well-drained sandy high ground and using grease, tallow, wax, or some other waterproofing agent to try to seal valuable goods.

The modern Mackinac Island geocache may be a plastic box with a tight-fitting lid. All of them will be hidden in locations that are a bit more than 45 degrees north, and a bit more than 84 degrees west, because that is the location of our Island on the earth’s surface.

Many GPS devices display locations in terms of degrees, minutes, and seconds; there are 60 seconds in a geographic minute, and 60 minutes in a geographic degree. Many readers will have already guessed that this way of finding one’s precise location in space started with primitive astronomers who carefully observed the sun. As the earth turns on its axis, the sun seems to move one “second” every geographic second. If you count up the geographic seconds it takes to go around the world, there are 86,400 of them, which are exactly the same as the number of seconds in each day. This is not a coincidence.

The French explorers who mapped the shores of America’s Great Lakes were often not trained in surveying. When we look at the maps they drew in the 1600s and 1700s, we can see many mistakes; Mackinac State Historic Parks owns copies of several of these valuable maps, and maybe a couple of them will be displayed soon in the new Richard and Jane Manoogian Mackinac Art Museum in downtown Mackinac Island.

Modern surveying had to wait, in any case, until the invention of a reliable chronometer watch that could be used to observe astronomical objects and precisely fix longitudes. We still say that there were “Three Flags at the Straits,” and you can see all three of them in summer on Mackinac Island at the Avenue of Flags, the feature designed by the late Eugene Peterson to welcome visitors to the upper entrance to Fort Mackinac. After the French flag comes the British flag, and every geocacher should know that their GPS devices are programmed with a key piece of information that dates directly back to the time the Red Ensign flew over Fort Mackinac.

The inventor who assembled the first longitudinal chronometer was an Englishman, a Mr. John Harrison, and he and his successors sold chronometers to the “sea dogs” of the Royal Navy – the fighting force celebrated in Patrick O’Brien’s novels. Starting in the late 1700s, the Royal Navy calibrated its chronometers by the longitude of its headquarters in Greenwich, a suburb of London, and the longitudinal numbers that flash on our GPS devices are based upon Greenwich to this day. If going around the world is a trip of 360 degrees, then on this transit Mackinac Island is 84/360 west of London, many thousands of miles but still not quite one-quarter of the way around the world.

Despite the Royal Navy’s achievements, the crown of Great Britain could not prevent the territory of Michigan from falling into the hands of the upstart Americans – the third of those three flags. In the first half of the 1800s, U.S. Army engineers, such as the future Civil War general George Meade, surveyed the shores of the Straits of Mackinac. Determining one’s precise location on Mackinac Island, which now can be done with the push of a button or two, then required tedious observations of several known angles – such as the elevation of the North Star – and then complex arithmetical calculations by the light of a grimy window, a candle, or an oil lamp.

Precise surveys of this sort created the necessary groundwork for siting and building the great necklace of lighthouses that sprouted up in these Straits in the second half of the same century. Beautiful beacons, such as the McGulpin Point Light that was re-lit last summer near Mackinaw City, could never have been built without the careful surveys performed earlier in the 1800s that were needed to draw printed maps and charts.

Geocachers who visit Mackinac Island are fitting into a rich history of mapping and survey work here.

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