346 Mr. George K. B. Elphimtone [Feb. 23, 



attention of many, but the credit of being the first to produce a 

 practical working instrument belongs to Dr. Anschiitz, who, with 

 those associated with him, has devoted some twelve years of patient 

 work and no inconsiderable sum of money in experiments. Since 

 then some important work has been done by Hartmann and Braun 

 in Germany, and Mr. Sperry in America, details of which are not 

 available. 



Few people have any idea of the difficulties attending the installa- 

 tion and correct adjustment of a magnetic compass on board a large 

 steel ship, and more particularly on a battleship or cruiser, so as to 

 work surrounded by huge masses of steel, and in order to withstand 

 the terrific shocks caused by the firing of heavy guns, and the 

 problem would to-day be impossible had it not been for the theoreti- 

 cal work of Sir George Airy, the applied genius of Lord Kelvin, and 

 the present practical improvements introduced by the Superintendent 

 of Compasses at the Admiralty. 



A magnetic needle can only point in the direction of the lines of 

 magnetic force at the place where it is set up, and it is well known 

 that there are very few places on the globe where the magnetic needle 

 points true North and South. 



Dr. Anschiitz attacked the problem of a Gyrostatic Compass with 

 enthusiasm, and has continued to work at it in the face of many and 

 great disappointments with a thoroughness and patience which is 

 characteristic of his nationality. The construction of the Compass 

 meant new designs for everything in connexion with its motors, 

 etc., etc. 



His first experiments were with Gyrostats suspended with the 

 Gyro free to move about its three principal axes, or, as it is termed, 

 having three degrees of freedom ; but it is easy to show how impos- 

 sible it is to construct such a Gyro so as to be sensitive to small 

 movements, and yet really accurate in practice. 



To make use of the gravity effect of the earth Dr. Anschiitz 

 mounts his Gyrostat in the form of a pendulum ; as the earth rotates 

 the Gyrostat tends to maintain its plane of rotation parallel to its 

 original plane in space. 



The earth's gravity acts against this tendency, and a precession 

 results, the only position of equilibrium occurring when the Gyro 

 axis has set itself parallel with the axis of rotation of the earth. 



Several models were shown to demonstrate this tendency, and to 

 illustrate how the Gyro Compass sets itself ^ovih. and South. 



In the actual Compass the friction of the universal joint carrying 

 the pendulum arrangement must be very small for the Gyro to take 

 an ultimate position with accuracy — the length of the pendulum, and 

 hence the effect of gravity, must be small, so as to keep the Compass 

 free from disturbances — and therefore the precession is very slow, and 

 the Compass would swing to and fro on either side of the meridian 

 indefinitely ; its mean position would, it is true, be the true North 

 and South Hue, but valueless for practical use. 



