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BULLETIN OF THE UNITED STATES FISH COMMISSION. 
SVEDBBRO’S MARINE GOVERNOR. 
In a heavy seaway a ship, from excessive pitching, will sometimes throw the 
screw out of water sufficiently to relieve it of the resistance of the water; at sucli 
times the screw and engine, thus released, will spin around very rapidly, endangering 
the machinery. To prevent this it was formerly the custom to station a man at the 
throttle, who would close it when the engine began to speed up (to “race”), and open 
the valve when the engine slowed down. This operation was never satisfactory, and 
gave birth to the invention of many marine governors, the majority of which were 
centrifugal in principle, and consequently depended on the speeding of the engine to 
close the throttle, or, in other words, to slow the engine after the racing had com- 
menced. Tlje object of the Svedberg governor is to antici]>ate the racing and to close 
the throttle valve before it commences. 
To accomplish this an air-chamber A is placed at the stern of the ship, as low down 
as it can be tixed; the top of this air-chamber is connected to the top of a mercury- 
cup by a pipe; this mercury-cup B, is made on the principle of a Wolf jar, and besides 
mercury it contains a wooden float on the lower end of the rod c, which passes through 
the oblique cylinder d to the surface of the mercury; the cylinder, though in the same 
casting with the mercury-cup, has its tower rim immersed in the mercury. Any 
elevation of the stern of the ship, or any rise or fall of the water under the stern of 
the ship, will increase or diminish the pressure in the air-chamber A, which pressure 
is iiromptly communicated to the mercury-cup B, and depresses or lifts the surface of 
the mercury in the cup; but as the lower rim of the oblique cylinder d is immersed 
in the mercury, any rise in B will depress the mercury in d, and will cause the float 
(and rod c) to fall or rise accordingly; and this rise or fall is directly proportional to the 
pressirre at the stern of the ship. The pressure exerted by the float is necessarily 
small, while the power required to move the throttle-valve is sometimes considerable, 
and for this reason a steam-engine is interi)osed, the float moving the valve of the 
little engine, while the pressure of steam in the little cylinder moves the throttle. In 
this engine the piston and rod are fixed, while the cylinder moves upon the piston ; the 
