1912] on the GyrostaUc Compass. 347 



One or two slides were shown illustrating the etfeot of the damp- 

 ing, and a model demonstrated how this was effeeted by the air-blast 

 set in motion by the (lyro itself. 



The sizes, weights, and speeds ohosen are such as to result in a 

 Compass having many times the directive force of a Magnetic Com- 

 pass, and therefore responding to much smaller alterations of direc- 

 tion than can readily be observed with a Magnetic Compass. 



The Compass itself being quite non-magnetic can be put down 

 under armour — in a position where a Magnetic Compass could work 

 only with very special precautions and under grave difficulties. 



The action of the contact is to control a small electric motor, 

 which moves a plate away from the contact on tlie card as soon as it 

 touches it, and then the motor stops ; the motor drives a transmitting 

 device which controls as many receivers as are wanted in the ship. 



A complete Master Compass was shown — which is destined for a 

 very celebrated war ship — and several receis'ers were shown in action, 

 an electric motor being attached to the binnacle so as to turn it round, 

 and so imitate tlie movements of a ship relative to the meridian. 



The receivers are merely electrical counters, and can be put in 

 any position ; the small dials make one complete revolution for only 

 10" change of course, and these are geared after the manner of clock- 

 hands to the outer dial, one turn of which corresponds to a turn of 

 thirty-two points, or 360° ; they are arranged to turn at a quicker 

 rate than any large ship can turn in the water. 



The movement which the inner card makes, for a very small 

 alteration of course, is considerable, and takes place instantly ; and, 

 owing to this fact, enormous improvement is possible in the steering 

 of a large ship when the helmsmen have become used to the appear- 

 ance of the dials. 



The diagrams on the screen showed actual records taken of the 

 courses in several large warships, and the varying amounts of helm 

 employed to maintain those courses. 



On the table was an actual recorder, electrically connected to the 

 receiver circuit from the Master Compass, and tracing the actual 

 movements which the binnacle makes to and fro. 



Attention was drawn to the necessity of corrections which have 

 to be applied to the readings of the Compass. 



The first correction is an interesting one, as it is not apparent at 

 first sight ; it is common to every form of Gyrostatic device which 

 takes the earth's rotation into consideration. 



If a ship with a Gyro Compass is steaming due East or due 

 West, the ship's speed is added to the speed of rotation of the earth 

 in space, or deducted from it. 



Suppose the ship steams due North, then the resultant travel of 

 the ship in space is along the diagonal line, as it is moving from 

 West to East by the earth's rotation, and South to North by its own 

 steam. 



