212 THE COMMERCIAL GYROSCOPIC COMPASS. 
The new compass is smaller and lighter than the battle gyro-compass, and is 
being developed in a still. smaller form for use on aeroplanes and small yachts. 
As built at present, it weighs only about 50 pounds, exclusive of the binnacle 
in which it is mounted, the complete weight with the binnacle being only about 
225 pounds. The smaller size will weigh only about 40 pounds when the aeroplane 
mounting is used, there being no binnacle. The overall diameter of the compass 
with the binnacle is only about 16 inches, and the weight about 100 pounds. 
Due to the small size of the wheels (the wheels used on the destroyer type are 
only 5 inches in diameter), the time required to bring the compass up to speed from 
rest is only about five minutes. 
If the ship upon which the compass is mounted is to be tied up at dock for 
some length of time, the switch may be opened and the compass allowed to come 
to rest; then if the switch is again closed about fifteen minutes before the ship 
is to sail, the compass will come up to speed and immediately settle upon the 
meridian. Of course, it is desirable to start up the compass earlier in order to 
give time for it to settle completely, but in some cases it may be a great advantage 
to be able to use it almost immediately after it has been started up. During one 
of the earlier sea trials, the supply switch was accidentally opened in the engine 
room and the compass had come to rest before this was noticed; but as the ship 
was on a straight course, the switch was simply thrown in, whereupon the compass 
came up to speed, and the first observation made showed it to be almost exactly 
on the meridian. The compass may also be placed on the meridian by hand before 
starting, in case the ship is at rest, and it will then come up to speed and be found 
to be on or very near the meridian without any further setting. 
The compass is designed with a view to reducing to a minimum any attention 
that may be required, making it unnecessary for the ship to have a man specially 
trained to care for it. For instance, it might easily be started up in New York and 
would not need inspection again until the ship reached Liverpool. 
In this connection it may not be out of place to state that in addition to guar- 
anteeing each compass, the manufacturers have trained compass experts in nearly 
all of the principal ports of Europe, each with full equipments, spare parts, etc., 
some seventeen operating out of the London office alone. It is the duty of these 
engineers to instruct officers and men as to the care and operation of the compass, 
and also to see to it that every compass coming into their ports is giving perfectly 
satisfactory service. 
In trial, and in fact all of the earlier voyages made by new steel ships, the 
gyro-compass should be employed, even if it must be under rental, because of the 
large changes that are constantly going on in the magnetic moments of new ships. 
When a new ship is constructed on her ways, the driving of the myriad of rivets 
tends to magnetize the entire structure very permanently and to a high degree. 
Lord Pirrie told the writer that it cost him the equivalent of $2,800 to take the 
Olympic sufficiently out to sea to enable her to be turned prior to receiving her 
engines and finish, solely on account of aiding the magnetic compasses in their 
