IV. PENDULUMS AND GYROSCOPES. 121 



IV. PENDULUMS AND GYROSCOPES. 



531. Gyroscope. A mechanical contrivance to exhibit the 

 phenomena of rotation, and to show experiments on the deviation 

 of spherical projectiles. Elliott Brothers. 



532. Foucault's Gyroscope. Ordinary model. 



Geneva Association for constructing Scientific Instru- 

 ments. 



53 2a. Gyroscope, by Foucault. College of France, Paris. 



532b. Reuleaux's Ball-Geometer. 



H. ffadicke, Engineer, Demmin, Pomerania. 



The object of the instrument is to indicate the rotations made per minute 

 by any rotating body brought into connexion with the same. The number 

 indicated will be read off a dial. As a remarkable peculiarity it may be men- 

 tioned that the scale of the dial shows a uniform division, although the 

 position of the balancing balls moving the pointing hand depends according 

 to a complicated law on the velocity of the rotation of the spindle (shafts). 



The motion is worked by means of straps and strap disc, and can, as a matter 

 of course (on vessels, &c.), be effected by a fixed connexion with a shaft- 

 movement. 



A winch-handle, however, will enable the spectator to put the instrument 

 in motion by the hand. 



The accuracy of the indications of the instrument will be augmented if the 

 pointing hand is turned off a little with the finger in the direction of the pro- 

 gressive numbers, and then allows it to jerk back freely. 



A forcible turning of the pointing hand in the opposite direction, toward O, 

 is not allowed. 



533. The Polytrope. A gyroscope mounted on circles so 

 as to prove the laws of combined rotations about several axes. It 

 may be used to determine the meridian or the latitude of a place, 

 and to show the rotation of the earth on its axis, and for other 

 experiments. 



Wheatstone Collection of Physical Apparatus, King's 

 College, London. 



534. <* Soldier Experiment." Model designed to demon- 

 strate the relative effects of revolution and of rotation, separate or 

 combined, by the movements of soldiers. 



Henry Perigal, F.R.A.S. 



535. Compass Experiment, demonstrating that a mag- 

 netised needle does, but an unmagnetised needle does not, maintain 

 its parallelism while revolving or orbitating in a circle. 



Henry Perigal, F.R.A.S. 



536. Gyroscope, demonstrating the effects of revolution and 

 of rotation, the two ways of turning round. 



Henry Perigal, F.R.A.S. 



