168 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



which it will vibrate if disturbed ; acting, in fact, precise- 

 ly like a common pendulum, except that the effect of grav- 

 ity has been greatly diminished, so that the time of vibra- 

 tion is increased. In the instrument actually observed by 

 Zollner the horizontal lever vibrated once in about fifteen 

 seconds when in its horizontal position ; whereas, if removed 

 from its supports, and vibrated vertically like a common 

 pendulum, it would have required a quarter of a second 

 only. The instrument was so susceptible to disturbing in- 

 fluences that it was set in motion by a railway train pass- 

 ing at a distance of about a mile. Zollner has suggested, 

 as did Gruithuisen before him, that it may be possible by 

 means of this instrument to determine directly the attraction 

 of the sun and moon upon it, and hence to determine their 

 distances. It may even afford a means of measuring the 

 time required by gravity to pass from the sun to the earth. 

 4 D, 1874, VII., 126. 



ELECTRO-TORSION. 



Mr. George Gore has shown that a rod may be brought 

 under the influence of electric currents in such a way as to 

 experience a twist amounting to as much as a quarter of a 

 circle. This twist is always attended by the emission of 

 sound, and is produced by the combined influence of heliacal 

 and axial currents of electricity, one current passing through 

 a long copper wire surrounding the bar, and the other in an 

 axial direction through the bar itself. The result is explain- 

 ed as due to the combined influence of the magnetism in- 

 duced in the bar by the coil current, and of the transverse 

 magnetism induced in it by the axial one. The current 

 flowing from a north to a south pole produces left-handed 

 torsion ; a reverse one, right-handed torsion, i. e., in the di- 

 rection of an ordinary screw. 4 D, VII., 419. 



ELASTIC REACTION BY TORSION. 



From a communication by Dr. Nessen, presented to the 

 Academy of Sciences of Berlin by Helmholtz, it appears that 

 the former has been investigating the reaction observed after 

 twisting a string of India rubber. This substance is pecul- 

 iarly interesting, because of its remarkable combination of the 

 properties of viscosity and elasticity. The observations of 



