coast defense

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Fort Andrews Mortar Batteries

At the outset, the principal armament of Ft. Andrews was intended to be its two batteries of 12-inch mortars. Battery Whitman, completed in 1902 (a full two years before the first gun battery, Bty Rice, which perhaps never had its guns installed), probably started out with eight mortars, and Battery Cushing, next to it and further east, mounted another eight. These were likely all M1890 mortars.

Each battery had two mortar pits. Battery Whitman's were one behind the other, runing south (Pit A) to north (Pit B), while Battery Cushing's were side by side (with Pit A furthest east). Cushing's pits measured about 83 ft. deep by 67 ft. wide; Whitman's were somewhat smaller, averaging 70 ft. deep by 69 ft. wide. In each of the four pits, there was generally about 29 ft. between the centers of the mounts for each morrtar.

A 1921 report indicated that Whitman mortars 1 through 4 (M1890 tubes in Pit A, closest to the road) had been upgraded to M1908s and that Nos. 5 and 7 (in Pit B) had been scrapped. An article in the Boston Evening Transcript of May 19, 1915 describes proof firings of a "new type of mortar" at the fort, whick likely pinpoints the installation date of the M1908 tubes. Then, by 1928, it was reported that Nos. 1, 3, 5, and 7 in Bty Cushing had been dismounted (leaving it with four M1890 mortars, two in each pit). A 1935 note confirmed this 6 + 4 alignment (Whitman + Cushing).

Studying the remains of equipment (in April, 2010) for firing the mortars electrically confirms these arrangements. Four armored cables run from the firing circuit switches outside the control booth at the northwest corner of Whitman Pit A to its four mortar positions, while each of the other pits has only two mortar cables and switches.

The current to fire the mortars electrically (they could also be fired by lanyard pull, using friction detonators) came from special"mortar magnetos mounted on the rectangular steel brackets that still appear on a wall in each pit.

The mortars could be fired either electrically or by a lanyard pull, depending on the type of detonator used. Several safety interlocks were built into the weapon and the electrical circuitry so that the weapon could not be fired accidentally or before it had been fully elevated.

First, the mortar could not be fired until its breech was fully closed. A safety bar or a circuit breaker served this purpose. A special safety catch kept a lanyard pull from reaching the primer until the mortar had reached a safe firing elevation.

To fire a mortar electrically, a plug from the magneto, located on a nearby wall of the pit (see Slide 12), had to be inserted into a plug box on the mortar, and this could not be accomplished until the mortar had been elevated to at least 45 degrees. This was done to avoid having the mortar fire while it was still depressed, such that its projectile would hit the wall of the pit.

The safety switch on the wall of the pit (see Slide 11) had to be closed for that mortar to enable it to be fired.

Finally, a spring-loaded lever in the firing handle of the firing magneto on the pit wall had to be squeezed by the person firing, and when he squeezed and pulled quickly on this handle, it produced the current needed to fire the mortar out in the pit.

Firing by lanyard worked as follows. After the mortar had been elevated beyond 43 degrees, a short lanyard could be attached to the firing leaf (and detonator). A long lanyard was then attached to that and pulled quickly by a person standing directly to the rear of the piece.


On early drawings, the small concrete booths in both Whitman's pits were labeled "telautograph booth." The Coast Artillery experimented briefly, during the 1920s, with a device, called the telautograph, that was designed to transmit written messages by wire from one position to another. The east side fire control building also had "telautograph" connections marked on its blueprints. Boston was selected as one of the first sites to receive this new technology, which was thought to be a way to transmit firing data from spotters to the batteries that could be understood even in the midst of the thundering din made by firing the huge mortars. However, it was discovered that the DC voltage supplied by the Coast Artillery generators to the to the telautographs was too variable to enable the sensitive instruments to work correctly, and the new technology was abandoned. [For a complete description, see the article by Bolling W. Smith in the November, 1996 issue of "The Coast Defense Study Group Journal," p. 19.]

The magazines for Battery Whitman lay in the gallery between its two pits; Battery Cushing's magazines surrounded the pits and appear to have been much more extensive. Battery Cushing also held the two 25KW generators that supplied power to the mortars and to the three gun batteries atop the eastern right. One of these generators was primarily dedicated to powering the 60-inch searchlight on the northern bluff of the island that illuminated the channel approaches in the direction of Ft. Warren.

There are photos of firing drill for the mortars that are said to date to the 1940s, and a news item of November 28, 1941 reports that target practice firings from Whitman-Cushing actually knocked windows out of a nearby barracks building and caused one of its doors to drop flat on the ground. The Army abandoned all the mortars just before Christmas, 1942.

During the years the mortar pits were in service, their surrounding slopes appear to have been totally bare of vegitation. Indeed, mortar firings are reported to have regularly set fire to the grass on the hillsides above the pits. Today, however, the sides and floors of the pits are fairly well covered with trees and brush. A picnic table, dragged in by kids for a party, sits in the middle of Whitman Pit B. And Cushing Pit A was about half filled-in several years ago with debris bulldozed-up by a contractor.


Video of The Firing Sequence

The remarkable video link in the sidebar at left shows (during its first three minutes) firing drill on four M1890 mortars of Bty Howe in the coast defenses of San Francisco, about 1915. [These mortars were identical to those of Bty Cushing.] A shell is wheeled up to the breech on a shell cart with several crew following it bearing a long ram. Once the shell is rammed in, a bright white-clad cylinder of powder (composed of a variable number of powder packets) is then inserted (often tossed) in beind the shell, a detonator is inserted, and the breech is cranked shut. The crew clears the immediate area of the mortar ("taking cover") as the barrel is elevated to firing position and the chief raises his arm, signalling ready to fire. The mortar is fired and then rapidly depressed so that the breech can be swabbed and the process repeated for the next round.

The video clip shows how rapidly the crew members move through their coordinated tasks. A good crew could fire two rounds per minute. The coreography of crew movement in a "square" (not "linear") battery such as those of Ft. Andrews would have needed to be even more precise, given the restricted space available for wheeling the shells up and ramming them home.

The Mortar Batteries

  • 12-inch Mortar M1908 Bty Whitman
    This photo, said to be of Bty Whitman, must then have been of Pit A, where the M1908 mortars were, and the viewing angle, which includes the concrete booth that was the pit officer's position, identifies this as mortar #3. Note the five-fold signaling device (withouit its "slats") visible on the left side of the pit officer's booth. These slats could be slid in or out from within the booth. These booth were also known as "telautograph booths," since for a while they contained this new device for transmitting firing data by wire [see Slide 2]. (Mortar photo courtesy of Gerald Butler, Harbor Islands, p. 57)
  • Telautograph
    This image, from Bolling Smith's article (see text) shows a transmitter (left) and receiver (right) for an early Coast Artillery model of this device, designed to transmit written information electrically from fire control positions to gun and mortar batteries. The hope was that this would avoid interference with telephone communications that was caused by the din of firing guns. The device proved to be unreliable under field conditions, due to variability in the voltage of power supplied by the on-site generators of the coast artillery forts. A "telautograph booth" is clearly shown in Slide 1.
  • 12-inch M1890 Whitman
    This photo, from the same source as that in Slide 3, is thus likely of one of the mortars of Bty Cushing, probably in Pit A, in 1941-42. This does not appear to be a firing drill, so perhaps the emplacement is being inspected. (Courtesy Gerald Butler, Harbor Islands, p. 88)
  • Whitman A Firing
    The Pit A placard is clearly visible, and since Bty Whitman's Pit A contained M1908 mortars, these M1890 weapons are assumed to have been in Bty Cushing. Fifteen shells are on shell carts are visible nearby, waiting to be loaded. (Courtesy of Gerald Butler, Harbor Islands, p. 87)
  • Bty Whitman Entry
    This image gives an accurate indication of the extent to which the battery is now under assault by undergrowth and crumbing slowly away. (PG 2010)
  • Whitman Pit A Lkng WSW-ly
    Looking at this image, it is hard to remember that this pit and its banks were originally completely bare. The pit officer's station is at center left, and the clumps of heavy undergrowth roughly indicate the four original mortar positions, in a square about about 30 ft. on a side. (PG 2010)
  • Whitman Pit A, Lkgn SE
    This view looks back across Pit A in the criss-cross direction to that of Slide 5. The street at upper right is the street running from the fire station westerly towards the mortar pits, and the cobbled concrete "apron" just outside the pit proper is visible at upper right on this side of the street. (PG 2010)
  • Whitman-A, Looking NE
    Photo looks NE from the road in front of Whitman Pit A. The westerly portal to the Whitman magazines is at the extreme left, at the back of the pit. The sun-drenched casemate entry once housing the plotting room for the battery. Farther east along the casemate are the doors to the twin 25KW generators that were located inside, and the small exterior structure housed the cooling radiators (with roof-mounted blowers) for the generators' engines. (PG 2010)
  • Cushing B-Shelter And Gallery Portal
    The portal to the right, now closed off to prevent public access, led to the galleries. The small blockhouse is the pit officer's station. Note the vegitation thickly covering the floor of the pit. (PG 2010)
  • Cushing Shelter And Semaphore
    This blockhouse sits just outside the NW edge of Pit B, Bty Cushing. Note the "semaphore" panels, now deteriorated, in the frame at left of the building. These could be slid out from within the blockhouse and reportedly carried range, azimuth, and zone (powder charge) data for the mortars (info from Mark Berhow, 2010). (PG 2010)
  • Control Box, Whitman-B
    The four switches in this box were likely safety switches that enabled or interrupted the electrical firing circuits to the mortars. Box is next to the pit officer's station of Bty Whitman, Pit B, which ended up with only two mortars, so only two cables lead out to the pit. (PG 2010)
  • Firing Circuit Control Switches
    This photo shows a switchbox similar to that in Slide 10, but this time near the magazine portal on the westerly side of Bty Cushing, Pit B. The niche with the armored door above and to the left likely held a telephone. The steel "holster" mount visible below the switchbox likely held an MA type firing magneto for the four mortars, which could be dismounted and taken in out of the elements when not in use. It appears that an arm on the magneto was pulled down, generating firing current, and firing any mortar in the pit for which the firing circuit switch was closed. The magneto was attached to the now severed cable to the left of the "holster" via a fitting that is now missing. The firing magneto weighed almost 90 lbs. (PG 2010)