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.