122 SEC. 4. KINEMATICS, STATICS, AND DYNAMICS. 



537. Gyroscope, demonstrating that revolution (orbitation) 

 alone will account for our always seeing the same face of the 

 moon. Henry Pcrigal> F.R.A.S. 



538. Selenoscope, to demonstrate the kinematic effects of 

 the three hypotheses of the moon's motion, as a satellite of the 

 earth. Henry Pcrigal, F.R.A.S. 



539. Kinescopes, illustrating the laws of compound circular 

 motion, by ocular demonstrations of their representative curves, 

 .shown by bright beads revolving with great rapidity. 



Henry Perigal, F.R.A.S. 



53 9a. Pendulum Apparatus, for the graphic representation 

 of the combination of non-rectangular vibrations, with illustrative 

 plates. 



Institute for Physical Science of the University of Halle, 

 Professor Dr. Knoblauch. 



An apparatus for the graphical representation of two simultaneous oscilla- 

 tions inclined to each other. 



To a table are fastened the axle-beds of two pendulums, the oscillation- 

 planes of which, are permitted to change their angle of inclination. One of 

 these pendulums transfers its motion to a horizontal bridge, the other to a 

 writing pin which moves exactly above the bridge. The oscillatory directions 

 of the bridge and the writing pin are the directions of the combined velo- 

 cities. The curve the pin writes down on the oscillatory bridge is to be 

 considered as the trajectory of a point moved across a reposing basis by the 

 simultaneous oscillations of the pin ami the bridge. 



One fixes this trajectory either by conducting a steel pin over a piece of 

 sooted paper, or leading over a white paper a narrow-pointed glass tube filled 

 with auilin ink. 



If the weights at the pendulums are displaced the proportion of their 

 oscillatory movements is altered ; every difference of phase is obtained by 

 an appropriate choice of the time, one pendulum begins to move after the 

 other. In this way the apparatus produces the greatest variety of geome- 

 trical figures imaginable. 



The tables accompanying the apparatus may serve as specimens, which 

 were draAvn by the apparatus. 



A more exact and scientific explanation is to be fonnd in the " Zeitschrift 

 " fur die gesammten Naturwissenschaften von Dr. C. Giebel," Bd. XIV., 

 October 1875. 



The apparatus has been projected by P. Schcanemann in the Royal Semi- 

 nary of Mr. Knoblanch, Professor of Physics at the University of Halle, and 

 has been executed for the physical science cabinet of the University of 

 Mr. Kleemann, mechanical engineer (Halle, Manergasse 6). 



539b. Compensatory Pendulum. 



Rohrbeck and Luhme, Berlin. 



539c. Tisley's Compound Pendulum Apparatus. 



Tisley and Spiller. 



539d. Donkin's Harmonograph, for compounding two 

 parallel harmonic motions. 



