Harbor Defense: Controlled Mines and the Mine Casemate

Harbor Defense: Controlled Mines and the Mine Casemate. . , During World War I, controlled mines (Image A) were laid in two separate fields across the Patapsco River ship channel. The first was between Fort Howard and Fort Smallwood and the second was between Fort Armistead and Fort Carroll. They remained in the river during the war to protect Baltimore Harbor from incursion by foreign naval vessels., The mines floated about fifteen feet below the surface. They contained one hundred fifty pounds of explosives and were laid in groups of 19. Each mine in a group was attached to a distribution box which was in turn connected to the mine casemate control panel via submerged electrical cables., The mines could be detonated either by direct contact with a ship or remotely by a signal from the controlling casemate., Controlled mines were a very important and effective component of American harbor defenses. Submarine mines, originally known as "torpedoes" were an American invention. These devices were originally used following the Civil War as an effective maritime defense, lethal to shipping, to protect harbor and channel entrances. A controlled submarine mine was composed of a water tight steel case containing explosive and a firing device, with an electrical connection to shore to trigger the detonation of the mine. The depth of the mine was dependent on the mooring line that was attached to an anchor., The concrete structure hidden in the trees behind this sign was the Mine Casemate (Image B). It housed control panels that were used to test and to fire the mines, storage batteries that provided power to detonate the mines and a diesel electric generator used to keep the batteries charged. Walk around behind the structure to see the entrance., How the Mines Protected Baltimore. Mines were laid in groups of 19 across the mouth of the Patapsco. Each group of mines was electrically connected to the mine casemate. Fort Howard's mine planter was the H.M. Wetherell., When enemy ships ◆ entered the river, observers in the two mine stations ★ determined the coordinates, distances and directions of the ships., As the enemy ships entered the mine field, personnel in the mine casemate could use the control panels to set the mines to detonate on contact with a ship or they could directly trigger each mine in a group based on position data from the mine in a group based on position data from the mine stations., When triggered, the mine would detonate. Any ships close to the explosion might be crippled or sunk.