1!U2] on the 0//rostatic Com})ms. 345 



allowed the lecturer to have this old piece of apparatus out of their 

 museum. 



■ It is of some interest to note that the success of the present Gyro 

 Artificial Horizon, which is really based absolutely on Searson's 

 original model, has taken place within the last six years, or 160 years 

 since Mr. Searson made his original model. 



The success of the present form is very largely due to the method 

 adopted of running a revolving Gyrostat in a small chamber from 

 which the air has been exhausted, so that the Gyro keeps in rotation 

 for time enough for practical observations to be made. 



There are, of course, many very important practical applications of 

 Gyrostats to determine the amount of a vertical angular movement, 

 and further to use such determination for controlling moving Iwdies 

 or keeping them level. 



By the kindness of Mr. Brennan a working model was shown 

 demonstrating the application of a Gyrostat in his important Mono- 

 rail Apparatus. 



As regards the Second. Section of the subject : Indication of direc- 

 tion in a horizontal plane : — 



Edward Seng, of Edinburgh, in the year 1.S36 mentions the 

 possibility of a revolving disc, or Gyrostat, being employed to indi- 

 cate direction. 



Sixteen years later Leon Foucault carried out his experiments, 

 with a pendulum to demonstrate the rotation of the earth, in the 

 Pantheon, in Paris, the pendulum swinging in a definite plane while 

 the earth rotated under it. 



Foucault experimented with Gyrostats to replace his pendulum, 

 to demonstrate the earth's rotation, the Gyrostat being delicately 

 suspended so as to maintain its plane of rotation fixed in space while 

 the earth moved under it. 



Springs have been used, and perhaps the most important of all the 

 practical applications of Gyrostats is the spring-driven Gyrostat used 

 to control the course steered by a torpedo ; there are prol)ably more 

 Gyrostats actually at w^ork in this application than any other. 



By the kindness of the Admiralty the lecturer was enabled to 

 show an actual Gyrostat used in a Whitehead torpedo. 



So long as the torpedo travels on the course originally assigned 

 to it the plane of rotation of the Gyro travels parallel to its original 

 plane ; but if the torpedo for any reason deviates from its course the 

 Gyro remaining on the old course, so to speak, operates one or other 

 of two small valves which control the admission of air to a small 

 cylinder, in which a piston moves attached to the rudder, so that if, 

 for instance, the torpedo deviates to the left, the rudder is turned to 

 the right, and vice versa, and in effect a zigzag course is produced ; 

 the more freely everything works the narrower the curved path of 

 travel. 



The problem of a practical Gyrostatic Compass has attracted the 



