[43] WORK OF STEAMER ALBATROSS. 647 



Anthracite coal per hour .,.,.- pounds.. 1,226 



< 529.2 



Indicated horse-power < 5 



( 534.2 



Coal, per indicated horse-power, per hour pounds.. 2.29 



The ship was docked in July at the Norfolk navy-yard. We found the 

 outboard valves in good order. A quantity of barnacles (Balamdce) 

 was found inside the cast-iron chamber of the injection-valve. We 

 found the zinc ferrules in the nozzle of the outboard blow- valve had 

 corroded but little, while the iron chamber appeared preserved. We 

 found the line-shafts, under the insulation tape, to be free from corro- 

 sion. This tape has beeu on the shafts two years. 



The annunciator, referred to in my last annual report, was duly com- 

 pleted, and has worked well during the year. 



A current of air blown into the bottom of the case (Plate VI) will 

 cause the little wind-mill at the top to revolve. This is mounted on the 

 vertical spindle, which has a screw-thread near its lower end which 

 gears into a toothed wheel ; this wheel, which is on a horizontal shaft, 

 carries an arrow on each end ; the back of the indicator is secured to 

 one side of the pilot-house, with a circular hole in the wood large enough 

 to move in ; the front arrow is visible from the deck and the back arrow 

 from the interior of the pilot-house. If a current of air, blown into the 

 bottom of the indicator, revolves the arrow ahead, it is manifest that 

 the direction of the arrow will be reversed if the current be reversed. 



To secure these positive blasts, a small blower (as in Plate VII) is 

 placed in the engine-room, parallel with the line-shaft, to which shaft 

 it is belted. If the engine goes ahead the blower delivers a blast, and 

 if the engine backs the blower induces an air current, and if the engine 

 stops the blower and current of air cease simultaneously. 



There is one of these machines for each of the main engines; their 

 action is positive and automatic, and they can make no mistake. 



On board the United States ships Boston and Atlanta there are 

 three of these indicators in each circuit, which consequently announces 

 the motion of the engine at as many different parts of the ship. To 

 connect the blower and indicators we use lead pipes. 



The inertia of a ship in motion is considerable, and it takes some- 

 little time for the ship to change her direction even after the engines 

 are reversed; it often occurs, in sounding and in dredging, that oppos- 

 ing wind and currents carry the ship from the desired position in ref- 

 erence to the wire; hence it becomes imperative for the commander to 

 know, promptly, if either engine has moved in the desired direction. 

 Damage due to mistakes either in striking or in interpreting the signals, 

 which hitherto occurred, have not occurred since the pneumatic indi- 

 cators have been used. The tax on the commander's mind in reconciling 

 the wind, waves, current, strains on and direction of the dredging wire, 

 while dredging in the great depths of the Gulf Stream is considerable, 



