At just 160 square acres of land, Rainbow Bridge National…

At just 160 square acres of land, Rainbow Bridge National Monument is one of the smallest units of the National Park Service. What it lacks in acreage it makes up for in size as one of the largest natural bridges in the world! Photo by Rosemary Polletta (

Swirling sandstone with smooth edges makes for a striking…

Swirling sandstone with smooth edges makes for a striking contrast in this remote section of Vermilion Cliffs National Monument in Arizona. Home to extraordinary formations, this area, known as White Pocket, is only accessible by ATV’s or 4-wheel-drive vehicles. Please bring plenty of your own water, proper hiking footwear, and a #TeamPublicLands mindset, that will leave this place for others to enjoy. Photo by Jessica Fridrich (

Each spring, the energetic and playful bison calves or…

  1. Each spring, the energetic and playful bison calves or “red dogs” join the
  1. herd
  1. . Standing out with their bright reddish-orange coats, their bursts of energy are magical moments. They fill the fields with awkward jumps, uncoordinated sprints, and joyful reactions as they learn and grow. Pictured here is a newborn red dog with mom, just minutes old, fighting against a slight breeze in an attempt to hold itself up for the first time. Photo Yellowstone National Park by Taylor Albright (
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In a few short months, alpine wildflowers will be decorating…

In a few short months, alpine wildflowers will be decorating the scene like this incredible shot of Mount Rainier National Park in Washington. Capturing dawn’s early light means rising well before the body wants to, but you’re rewarded with extreme quiet and time to enjoy the sunrise. Recreate responsibly Photo courtesy of Nathaniel Wise.

Whooo let the kids out? Whoo whoo whoo! A burrowing owl family…

Whooo let the kids out? Whoo whoo whoo! A burrowing owl family at the Sonny Bono Salton Sea National Wildlife Refuge in California emerges from their artificial burrow. The burrows, dug by volunteers and refuge staff, give the owls a perfect place to raise their families. Photo courtesy of Wendy Miller.

When you’re known as “The Jewel of Lake…

When you’re known as “The Jewel of Lake Superior,” you have a lot to live up to.
Apostle Island National Lakeshore in Wisconsin features a combination of spectacular natural beauty and rich cultural history.

The islands are a sacred homeland for the Ojibwe people who live throughout the Great Lakes region. According to their written and oral history, they are the original inhabitants of this area and consider Madeline Island an important part of their past and present day lives. The Ojibwe call Madeline Island “Moningwunakauning” or “Home of the golden-breasted woodpecker.” Photo by Michael DeWitt (

Known for its history, picturesque blue waters, superlative…

Known for its history, picturesque blue waters, superlative coral reefs, and the vast assortment of bird life that frequents the area, Dry Tortugas National Park is an isolated gem surrounded by a wilderness of ocean.

Dry Tortugas lies at the farthest end of the Florida Keys. The colorful corals, sea grass, and reef fish that call this watery wonderland home, are some of the most vibrant in the world. Photo by National Park Service

Marine Chronometers: The Clocks That Changed the Course of Globalization


Marine Chronometers: The Clocks That Changed the Course of Globalization

A marine chronometer by John Harrison, crafted between 1761 and 1800. (Photo: Bjoertvedt via Wikimedia Commons [CC BY-SA 3.0])

Traveling across time zones can be disorienting—watches, clocks, and even your sleep schedule need adjusting to a new longitude. This problem faced by modern travelers had more serious implications in the 18th century—a time of fierce imperial competition on the high seas. As ships traveled east and west through different longitudes, their clocks were not able to maintain accurate time. As calculating time differences was a reliable way to determine the longitudinal coordinates of a ship, faulty time-keeping resulted in vessels getting lost and wrecked. The invention of accurate marine chronometers changed the course of seafaring and navigation forever.

In the early 18th century, sailors could measure latitude using the sun and stars. However, there were no accurate means to determine the longitudinal coordinate of a ship’s location. It was known that the coordinates could be calculated mathematically by comparing two accurate times—one at a known longitude and the other at an unknown point. Unfortunately, the pendulum clocks of the day could not be counted on to keep reliable measures when subjected to the rolling of a ship on ocean waves. After several naval disasters resulted from poor navigation, the British government offered a reward for technical solutions to the problem of longitude. The Longitude Act of 1714 offered £20,000 ($26,302) to anyone who could devise an accurate method of calculating the location of a ship within one half degree.


Frodsham Chronometer Clock


Marine chronometer by Charles Frodsham, London, circa 1844 – 1860. (Photo: User:Ktr101 via Wikimedia Commons [CC BY-SA 4.0])

Clockmakers set out to win the prize money by inventing a marine chronometer which could keep accurate time aboard a vessel. The English carpenter and clockmaker John Harrison eventually won the prize, and he is credited with the invention of the first accurate marine chronometer. In 1728, Harrison began to build his first prototype clock, known as H1. By 1736, the administrators of the prize—the Board of Longitude—were intrigued enough to order a sea trial of his first model. Pleased with the initial results, Harrison was awarded grants to continue refining his mechanism for improved accuracy. The clockmaker built models H2 and H3 over the next two decades. These models used springs and balances rather than the classic pendulum; however, the accuracy of each chronometer was still slightly lacking.

Harrison’s big break came with his fourth model, H4. In the mid-1750s the inventor decided to craft his next sea clock as a watch, rather than the earlier bulky models. In 1761, the Board tested H4 on a trans-Atlantic voyage. The results were shocking—the sea watch kept almost perfect time. Arriving in Jamaica, the watch showed a local time only five seconds behind the true time. The calculations of longitude made from the time kept on H4 were accurate to within one nautical mile. Unfortunately, the Board and the English Parliament were not immediately convinced of the watch’s accuracy. It took a fifth model, H5, and personal intervention by King George III before Harrison received the prize money for his life’s work.

The impact of the sea watch—or marine chronometer as it came to be known—was enormous. Navigation capabilities were greatly improved for explorers of the 18th and 19th centuries. The infamous explorer Captain James Cook used a replica of the H4 watch on his travels, finding it exceptionally accurate. While electronic GPS systems have mostly replaced the marine chronometer today, some sailors are still required to learn the method during naval service or certification processes. Chronometers today are encountered particularly in the tradition of Swiss watches, where the term denotes precision and accuracy.

If you would like to learn more about this clock which changed the world, scroll down to watch a video from the BBC.

The invention of the marine chronometer—or sea watch—changed the possibilities of navigation on the high seas during the late 18th century.

Inside h4 Clock


Inside Harrison’s H4 sea watch. (Photo: Mike Peel via Wikimedia Commons [CC BY-SA 4.0])

Invented by Englishman John Harrison, the marine chronometer allowed sailors to keep accurate time despite the rolling of the sea and while moving through time zones.

John Harrison


Portrait of John Harrison (1693-1776), English clockmaker, by Philippe Joseph Tassaert. (Photo: Wikimedia Commons [Public domain])

Harrison was inspired to invent the sea watch by prize money—the British Longitudinal Act of 1714 offered £20,000 to whoever could solve the problem of accurately determining longitude at sea.

John Harrison Designs For h4 Sea Watch Chronometer


An 1802 rendering of John Harrison’s H4 Sea Watch. (Photo: Wikimedia Commons [Public domain])

To determine longitudinal coordinates, sailors needed to know the accurate time at their location for a mathematical formula.

H3 John Harrison Sea Clock


John Harrison’s H3 Sea Clock timekeeper. (Photo: Bin im Garten via Wikimedia Commons [CC BY-SA 3.0])

Harrison’s fourth attempt—the sea watch known as H4—was accurate to within five seconds of the real time during a test voyage to Jamaica. This allowed very accurate calculations of the ship’s coordinates.

Although it took much persuasion and a fifth version of his sea watch for Harrison to receive his prize money, the marine chronometer quickly became an indispensable part of sea navigation.

Marine Chronometer


Harrison’s H5 marine chronometer. (Photo: Racklever via Wikimedia Commons [CC BY-SA 3.0])

Watch as the BBC unravels the fascinating history of the marine chronometer:


A visit to the @mypubliclands areas of the Sierra Nevada in…

A visit to the @mypubliclands areas of the Sierra Nevada in California can recharge the soul and awaken the senses. Writer Alice Walker said it best, “In nature, nothing is perfect and everything is perfect.” Filled with lush wildflowers and picturesque mountains, the Sierras are nature’s perfection. Photo by Bob Wick Bureau of Land Management

A life giving mentor…