THE GYROSTATIC COMPASS. 1 



[With 3 plates.] 



By H. Marchand. 



The gyrostatic compass may be looked upon as one of the most 

 interesting inventions made during recent years. 



The gyroscope is familiar to all. Nor are we ignorant to-day of 

 the fundamental laws which govern it. The great physicist Fou- 

 cault first completely formulated them as the result of his profound 

 researches on the subject. 



The first of these laws is that a gyroscope with perfect freedom of 

 movement — that is, the power to move in any direction, and free from 

 the action of gravity — will tend to maintain the initial position given 

 to it. The second law is that if a gyroscope has only two degrees of 

 freedom, in such a way that it can undergo displacement in two planes 

 only', it must, if subject to the action of gravity, and provided that it 

 is not at the poles of the earth, tend to place itself so that its axis is 

 parallel to that of the earth and accordingly will indicate the direc- 

 tion of true north. 



A system of this kind is free from the errors which affect the mag- 

 netic compass, and therefore the idea of taking advantage of it for 

 navigation must have early attracted the attention of investigators, 

 especially as the general use of steel in the construction of vessels 

 entails grave difficulties in the use of magnetic instruments. 



Formerly the means at hand were insufficient for constructing a 

 satisfactory, practical instrument, and so, during the time of Foucault, 

 and even much later, the numerous scientists who approached the 

 problem did not meet with much success. 



A German investigator, Dr. Anschutz, has recently succeeded in 

 constructing an instrument on gyrostatic principles which is prac- 

 tical. In 1900 he commenced the study of a gyroscope with perfect 

 freedom of movement. Later, however, in 1906, he abandoned that 

 for one having only two degrees of freedom. 



Even with the latter conditions the problem required great nicety. 

 A grave difficulty comes from the fact that such a device is affected, 

 under ordinary circumstances, not only by the rotation of the earth 

 but also by all the forces to which it is subjected because of the rolling 



» Translated by permission from Cosmos, Paris, New Series No. 1385, Aug. 12, 1911, pp. 181-184. 



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