286 THE SPERRY GYRO-COMPASS IN SERVICE. 



stars cannot be obtained, due to fog or other atmospheric conditions, navi- 

 gation in the vicinity of land becomes dangerous when using the approxi- 

 mate magnetic compass. 



The development of the gyro-compass will obviate the necessity for 

 studying the volumes on the theory of deviation of the magnetic compass 

 and the methods for determining its numerous coefficients, the nightmares 

 of the navigator. It will also be an end to the elaborate and time-consuming 

 evolution known as swinging ship. and compensating. 



On ships of war the magnetic compasses in the conning tower, steer- 

 ing engine-room and other battle stations are of little use for steering 

 the ship because of their extreme sluggishness due to the surrounding masses 

 of magnetic material. The development of the gyro-compass and its second- 

 ary transmission system makes it possible accurately to navigate and 

 maneuver the ship from any of these battle stations. Because the secondary 

 transmission stations are portable, it is possible to establish temporary 

 battle stations in lee of turrets or in other protected positions and use the 

 telephone for controlling the movements of the helm. As the master 

 compass, or heart of the gyro-compass system, is so effectually protected 

 against gunfire as to prevent its destruction without sinking the ship, it 

 provides a means for accurately handling a ship throughout an engagement 

 and for navigating it into port after the engagement. 



In this instrument we now have a compass that will reaUy fulfil Victor 

 Hugo's characterization of it as "the soul of the ship." 



The necessity for eliminating chance is an imperative law which is 

 fundamental to progress in every science. 



What an important and wonderful advance has been made in the 

 perfection of the gyro-compass. The guidance of our ships at sea has been 

 dependent upon the uncertain magnetic force of the earth. This accurate 

 instrument frees us from this dependence and gives us a means of precision 

 for guiding and protecting our ships and the millions of people which they 

 carry. 



The French physicist Foucault was the first to analyze the phenomena 

 of the gyroscope which underlie its application as a compass. This he did in 

 1 85 1 when he used the gyroscope for demonstrating the rotation of the earth. 

 His efforts resulted in the deduction of two laws which bear directly on the 

 use of the gyroscope as a compass : first, that the inertia of a rapidly rotating 

 wheel, suspended with freedom to move about all axes, is relative to space, 

 and consequently that a gyro suspended in that manner will maintain its 

 plane of rotation in space ; second, that a gyroscope suspended with its axis 

 of rotation horizontal, and with freedom about the horizontal axis partly or 



