APPENDIX. 923 



manner, so that the fixed points cannot vary. All the suspended apparatus is 

 electro-gilt. 



430a. Photograph of Electrodynamometer. Made by 

 Professor H. A. Rowland, John's Hopkins University, Baltimore, 

 on the model of that of the British Association. 



Cavendish Laboratory, Cambridge. 



484a. Two Hour Glasses. These were used in Spanish 

 men-of-war at the beginning of the last century. 



Ministry of Marine, Madrid. 



484b. Chronometer, the fifth made by the English maker 

 Arnold. It was used on board one of the Spanish ships at the 

 battle of Trafalgar. Ministry of Marine, Madrid. 



5O5. Discussion on Electro-ballistic Apparatus. 



539e. An Apparatus for the Graphical representation 

 of Two simultaneous Oscillations inclined to each other. 



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. 



564b. Kinematic Compasses with Three Branches, 



designed by Reuleaux. 



Royal Academy of Industry, Berlin, Director, Prof. F. 

 Reuleaux. 



By means of this instrument it is easy when the orbs of two points of a 

 system are given, to find all the other curves of the same system. 



(See Reuleaux's " Kinematik," s. 24, and following.) 



The third branch of these compasses may be altered longitudinally, and is, 

 besides, provided with a joint, so that entirely obtuse angular triangles 

 (amblygons) as well as entirely acute-angled triangles (oxygons) can be 

 taken by the compasses, for which the three-branched compasses of older 

 construction were not adopted. 



These compasses were manufactured by J. Kern, mechanical instrument 

 maker at Aarau, Switzerland, by order of he exhibitor. 



585a. Objects lent by M. Golaz, 24, Rue des Fosses, St. 



Jacques, Paris : 



Regnault's Eudiometer; Regnault's apparatus for measuring 

 the co-efficient of expansion of gas; Fabre and Silbermann's 



