184 REPORT OF NATIONAL MUSEUM, 1921. 
various purposes, including a magnetic compass, a master gyroscopic 
compass, a chronometer, a sextant, a pelorus, a patent log, a sound- 
ing machine, a hand lead, a stadimeter, and an aneroid barometer. 
These illustrate in an excellent manner the character of the delicate 
and complex machinery by means of which the modern ships of war 
are managed. 
The exhibit of the Navy Department also contains a number of 
typical pieces of ordnance of the type used during the war, as the 
6-inch gun from which was fired the first American shot during the 
war, and the primer which fired the last shot on November 11, 1918, 
at 10 o’clock 57 minutes 30 seconds, and examples of regular types 
of naval guns, as a 1-pounder rapid-fire gun on a boat cage stand 
mount used on the bows of .boats when employed in landing armed 
detachments or on harbor patrol; a 3-inch Davis nonrecoil 13-pounder 
gun used on small patrol vessels having decks too light to stand the 
shock of recoil of the usual type of guns; a 3-inch 50-caliber anti- 
aircraft gun; anda Y gun or depth-charge projector used to attack 
submarines. Of particular interest in this connection are unique 
models, complete in every detail, of the long-range naval guns on 
tractor and railroad mounts used in France during the war, includ- 
ing the 7-inch naval tractor and the 14-inch naval railway batteries, 
marks 1 and 2. In connection with these guns are a number of fire- 
control instruments, including a bore-sight telescope, a gun-sight 
telescope, a gun-sight check telescope, a short-base range finder, and 
a turret periscope. Other ordnance materials of note are projectiles 
of the type used by the Navy during the war—a number of aircraft 
bombs; 12, 8, 7, 6, 5, 4, 8, inch shells; 6, 3, and 1 pounder gun pro- 
jectiles; and a number of torpedoes and torpedo tubes. 
Of special interest are a number of pieces of the delicate yet power- 
ful signaling apparatus used during the war on naval airplanes and 
ships. These include a radio-telephone set, a radio compass, and 
specimens of receiving and transmitting vacuum tubes. A very strik- 
ing exhibit in this connection is a set of hydrophones for the detec- 
tion of the proximity of submarines, mounted on a model of a ship’s 
stern. 
The Navy Department has also deposited a number of pieces of 
captured German naval material. The most interesting of these 
are the engines of a German submarine, complete in every detail, 
a torpedo, and seven naval-gun shells. 
As may be noted from the foregoing summary, the exhibit already 
deposited by the Navy Department relating to the great war is most 
striking and presents in a graphic manner the leading features of 
the work of that branch of the service during the great conflict. 
This exhibit is constantly receiving additions of note and will un- 
