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



544. Wheatstone's Wave Apparatus. A complete in- 

 strument, showing plane, circular, and elliptical waves, the pheno- 

 mena of interference, &c. Elliott Brothers. 



544a. Apparatus to illustrate Wave Motion. 



Rohrbeck and Lwkme 9 Berlin. 



544b. Apparatus to illustrate Waves and Nodal Vibra- 

 tions of a row of Mutually Influencing Particles. 



Sir William Thomson* 



Each particle has only one degree of freedom, and is influenced by a force 

 depending only on the relative positions of itself and of its next neighbours 

 on each side. The shorter the wave-length the smaller the velocity of 

 propagation of the wave. 



The apparatus consists of a series of light rods loaded at each end, and 

 strung transversely on two threads which form, a bifilar suspension placed 

 equidistant from the centre of gravity of each rod. The distance between 

 the threads at any point is inversely proportional to the square root of the 

 tension at that point. 



545. Illustrations of Vortex Motion. Nos. 1 and 2 are 



vibrations ; Nos. 3-5 steady motion. (Proceedings of Royal 

 Society of Edinburgh, 1 November 1875.) Sir William Thomson. 



Series of 11 successive figures of a simple vortex ring, performing violent 

 transverse vibrations of the first fundamental mode. 



No. 2. Series of 1 1 successive figures of a simple vortex ring performing 

 violent transverse vibrations of the second fundamental mode. 



In Nos. 3-6 the motion is analogous to that of screw propellers backing, 

 the vortex core being in each instance as it were the edge circumference 

 of the screw propeller. 



No. 3. Two-bladed screw. 



No. 4. Three-bladed screw. 



No. 5. Four-bladed screw. 



No. 6. Trefoil knot described in Sir W. Thomson's papers on Vortex 

 Motion (Transactions of Royal Society of Edinburgh for 1857 and 1858), and 

 figured on the back of the " Unseen Universe," by Professors P. G. Tait and 

 Balfour Stewart. 



VI. FALLING BODIES AND PROJECTILES. 



546. Drawing of a new Apparatus for demonstrating the 

 lateral deflection of rotating conical projectiles. %\ 



Dr. Leopold Pfaundler, Innsbruck. 



The conical projectile A turns within the horizontal frame B on its own 

 horizontal axis, and can be put in rotation by pulling off the reel the string 

 attached to a. Fastened, on the outside of the frame, on two little hooks, b, //> 

 whose line of communication is perpendicular to the axis of rotation and passes 

 through the centre of gravity of the entire body, are two threads, which join 

 further up, and whose combined continuation is attached to a hook in the 

 ceiling. 



At the back there is a steering vane C with a counter-weight D, attached 

 in such a manner that according to the position in which it is placed the line 



