150 



SEC. 4. KINEMATICS, STATICS, AND DYNAMICS. 



Fig. 2. 



It is easy to understand that these hooks, when 

 " the handle is turned, perform two simple vibra- 

 tions, the one being invariable, the other variable, 

 in amplitude, phase, and velocity. 



4. From A and B proceed two strings, passing 

 through the pulleys C and E, and fixed in F and H. 

 These pulleys have strictly the same motions as 

 A and B, but reduced in the ratio one half. A 

 third string proceeds from A to B, passing through 

 D. At any moment the displacement of D will 

 be the sum of the displacements of A and B, re- 

 duced one half. Its motion is therefore the resul- 

 tant of the displacements of C and E. 



The motions of the three pulleys are shown 

 by the little white balls, placed on the front of 

 the instrument. 



5. With this apparatus an infinite number of combinations can be demon- 

 strated, of which the following are examples : 



. Two vibrations of the same amplitude and velocity, no difference of 



phase. The middle ball has double the amplitude. 



b. The same, the difference of phase being 180. The motion of the 

 middle ball is nearly zero. The deviation that will appear results 

 from the difference in the length of BD and CD (Fig. 1). 



c. Combinations of a tone with one of its harmonics 2 and 3 with its 



quint , or its quart , as well as when they are of the same intensity 

 or not (theory of the timbre). 



d. Combinations of two tones of the same intensity, with the interval if-, 



showing the origin of beats. 



541. Apparatus, of a new form, to illustrate Wave Motion. 



C. J. Woodward. 



This apparatus consists of a series of balls suspended from a horizontal 

 beam by strings. These balls rest against a series of partitions in a wedge- 

 shaped horizontal trough, which can be raised and depressed parallel to itself. 

 The box, being drawn on one side in the plane in which the balls hang and 

 then slowly depressed, the balls will be successively liberated, and a wave, 

 similar to that of the sound wave, produced. If the beam be drawn aside 

 prior to depressing the box, the balls will rest against one side of the trough 

 and can be liberated in succession, causing them to oscillate in a plane at 

 right angles to the beam, a vibration being produced similar to that of plane 

 polarized light. 



1576f. Wheatstone Wave Machine. 



The British Telegraph Manufactory, Limited. 



541a. Wheatstone's Apparatus, for illustrating the com- 

 position of rectangular vibrations. 



The Council of King's College, London. 



542. Drawings of new Apparatus for demonstrating the 

 composition of Vibrations. Dr. Leopold Pfaundler, Innsbruck. 



Plate I. Two blackened glass discs are each placed on a separate horizontal 

 axis one before the other, in such a manner that the transparent curves 

 apparently cut in their periphery, intersect each other nearly at right angles. 

 A reflection of light is produced thereby, which, at the revolution of the discs, 



