THE GYROSTATIC COMPASS—-MARCHAND., 43 
tric motor, and entirely free to turn in any direction were it not for 
two small springs, which serve to represent the attraction due to 
gravity and tend to keep the gyroscope’s axis tangent to the surface 
of the sphere upon which it is mounted. This apparatus may be 
slipped along a large movable metallic circle representing a meridian. 
When the springs are detached the axis of the gyroscope tends to 
take an invariable direction and to depart from it only because of the 
inevitable friction which is present at the pivots. 
However, once these springs are attached, if the meridian circle 
is moved to another place on the globe, then the axis will change so as 
to come into the plane of the circle, one of its extremities being directed 
toward the upper pole of the circle. According to the direction of 
the gyroscope and that 
of the circle, one or the 
other end of the axis 
moves so as to point to 
this upper pole. 
In the Anschiitz 
compass, of which fig- 
ure | is asectional and 
plate 2 a perspective 
view, the gyrostat is 
similarly driven by a 
three-phase electric 
motor; the float from 
which the gyroscope is 2 
suspended is a hollow Fira. 1—Anschiitz gyrostatic compass. Vertical section. A, three- 
Beg cipal partially, .isot tise t ahha cae cere 
immersed in & mer- float, floating in the mercury Q and counterbalancing the weight 
Z . of the moving system; K, compass box, suspended as usual by 
cury bath contained in gymbals; S, T, special suspension, made of two insulated conduct- 
an annular box also of ors for leading in two branches of the three-phase current, the third 
ste el T 0 th a + op of circuit being made through the floating ring and the surrounding 
this float is fixed the 
compass card. The north-south line of the card coincides exactly 
with the direction of the axis of the gyrostat. 
The small motor which rotates the gyrostat disk is so constructed 
that its stationary part is built on the box of the gyrostat. The 
electrical connections to the exterior are made for two of the circuits 
through small cups of mercury. The third circuit passes through the 
mercury bath containing the float and then through the case itself. 
The rotor is rigidly built on the gyrostat disk. It is of one piece, 
spindle and all, and made of nickel steel. It is provided with ball 
bearings of extra-hard steel and makes 20,000 revolutions per min- 
ute. The axle is of the Laval type or ‘‘flexible axle.” Its great 
38734°—sm 1911——8 
