Lamps and Lenses: How Old Mackinac Point Shed its Light Posted December 17, 2012 What puts the light in a lighthouse? Until 1913, a single lamp provided the light for the beacon at the Old Mackinac Point Lighthouse. This lamp is similar to the one used in the first 20 years of the lighthouse’s existence. It was eventually replaced with a gas lamp and then an electric light. This diagram shows how even a small amount of light from the lamp could be magnified using a number of prisms in a Fresnel lens. (Click to enlarge) Like most other lighthouses in the United States, Old Mackinac Point used a kerosene lantern not unlike those still found in many homes today. Keeper George Marshall’s duties included regularly fueling the lamp, as it burned over 5 ounces of kerosene per hour. A red glass lamp chimney originally produced a red light, helping sailors identify Old Mackinac Point. Both the kerosene lamp and red light were replaced in 1913, when the U.S. Lighthouse Service installed an incandescent oil vapor mechanism, which produces a white light similar to a modern camping lantern. While the kerosene lamp itself shone brightly, a fourth-order Fresnel lens amplified the Old Mackinac Point light until it was visible to a distance of 16 miles. The lens contained a series of stacked magnifying glasses around its center, with each glass focusing the light from the one beneath it. Prisms ringed the lens above and below the magnifying glasses. These prisms caught and bent more light, focusing it into the central beam created by the magnifiers. The entire lens rotated around the lamp, creating a flashing signature (one flash every 10 seconds) unique to Old Mackinac Point.
French Fireplaces of Michilimackinac Posted December 4, 2012 Shown on the left are the ruins of the original fireplace for the South Southwest Rowhouse at Colonial Michilimackinac. To the right, a reconstructed version and part of a new exhibit. The ongoing reconstruction of the South Southwest Rowhouse at Colonial Michilimackinac is an impressive undertaking. It’s the largest in the site’s history, the first in more than two decades, and when completed, will house two new exhibits. One of the featured components of the new exhibit “France at Mackinac” are the ruins of the original fireplace from the structure constructed more than 250 years ago. This particular fireplace is one of the few remaining structures left standing after British soldiers demolished the fort in 1780-81. As part of one of the longest ongoing archaeological digs in North America, the remnants of the rowhouse and the fireplace were carefully excavated over a number of years from 1963 to 2007. Stone fireplaces such as this were found in nearly every house at Michilimackinac, but this is the only one that remains because it was covered and preserved in a hill of sand soon after the demolition. Located in the west side of the building, the structure of this fireplace ruin served as a model for Tom Smith and his crew from Ground Level Masonry to create a similar fireplace on the east end of the building, showing how the stone hearth would have looked when originally built around 1750.
Today in History: Old Mackinac Point Lighthouse Fog Signal Sounded Posted November 5, 2012 On this day in 1890, Keeper George Marshall sounded the fog signal at the Old Mackinac Point Light Station for the very first time. This first blast of the fog whistle signaled the completion of a project begun a year earlier. In March 1889, Congress passed two acts regarding the creation of a light station at Old Mackinac Point. The first formally established the Old Mackinac Point Light Station, while the second appropriated $5,500 for the construction of a fog signal. This photograph from the early 1900s shows Old Mackinac Point Lighthouse and the fog signal building. The inset image shows the two steam whistles next to the boiler vent stacks. The fog signal sounded on November 5, 1890 was mounted on a 20’ by 40’ corrugated iron building. Inside, two identical steam boilers and associated machinery powered 10” steam whistles, which were mounted above the roof of the building. Although only one boiler and whistle were used at a time, keepers maintained the second set of machinery as a backup system. To help sailors identify the Old Mackinac Point fog signal, the fog whistles automatically sounded in a unique pattern: a 5-second blast, followed by 17 seconds of silence, followed by another 5-second blast, followed by 33 seconds of silence. Other light stations sounded their own unique whistle signatures. The U.S. Lighthouse Service replaced the original 1890 fog signal building with a brick structure in 1907. New boilers and whistles were installed in this building. The fog whistles at Old Mackinac Point may have sounded like this: Click here to listen to a steam whistle. The fog whistles themselves were replaced by air horns in the 1930s. Click here to listen to the fog horns at Old Mackinac Point Click here to hear it. Click here for more information or to purchase a copy of one of Mackinac State Historic Parks‘ Old Mackinac Point Lighthouse publications.
Old Mackinac Point Lighthouse Celebrates 120th Anniversary Posted October 25, 2012 Today marks the 120th anniversary of the first lighting of Old Mackinac Point Lighthouse in Mackinaw City. Workers pose outside the nearly completed Old Mackinac Point Lighthouse. Keeper George Marshall first lit the light on October 25, 1892 and workers completed the construction two days later. Old Mackinac Point Lighthouse remained an active lighthouse until navigation beacons on the newly completed Mackinac Bridge replaced it. The lighthouse is still open from May through October with guided tower tours, period exhibits and historic costumed interpreters. Click here for more information on visiting Old Mackinac Point Lighthouse.
South Southwest Rowhouse Construction Continues Posted October 23, 2012 After starting in October of last year, the construction on the South Southwest Rowhouse at Colonial Michilimackinac in Mackinaw City is making great progress. Two new exhibits and all new restrooms are planned for the structure, the largest in the history of reconstruction at Colonial Michilimackinac and the first in 23 years. With the completed construction of the roof, dormers have been added facing what will be the gardens. The ruins of an original hearth will be featured in a new exhibit about the French presence at Colonial Michilimackinac and the architectural style of the period. The walls and preliminary plumbing for the restrooms are in position.
