1891.] On Alternating Electric Currents. 255 



and that there is concealed within it, as a sacred mystery, the true 

 value of the precession of the Equinox. 



Chapter I. On the revolutions of the celestial bodies ; their mean 

 sidereal and synodic periods, as compared with the same elements 

 in modern tables. Mean places at a given time. On the Earth's 

 diameter, &c. On the Moon's horizontal parallax and distance from 

 the Earth. 



A theory deducing the orbits of the planets and the extent of the 

 Universe, or Brahmanda, from the Moon's daily rate of motion in 

 her orbit. 



Theory regarding the causes of the planetary motions, &c. 



Chapter II. On trigonometrical formulae known to the Hindoos. 

 The construction of their tables of sines and versed sines. On the 

 epicycle and its deferent, and on the eccentric and concentric, used 

 for calculating the " true " place of a planet from the mean place. 



Chapter III. Problems in astronomy, on time, ascensional differ- 

 ence, decimation, celestial longitude, horoscope, &c. 



Chapters IV, V, VI. The calculation and projection of lunar and 

 solar eclipses. 



Conjunctions, heliacal risings and settings, stars of the Zodiac, &c., 



The lunisolar year, &c. 



The cycle of Jupiter of 60 years. 



V. 4t Repulsion and Rotation produced by Alternating Electric 

 Currents." By O. T. WALKER, B.A., B.Sc., Fellow of 

 Trinity College, Cambridge. Communicated by Prof. J. ,T. 

 THOMSON, F.R.S. Received November 5, 1891- 



[(Abstract.) 



In the 'Electrical World,' May, 1887, p. 258, or the 'Electrical 

 Engineer ' (New York), June, 1887, p. 211, " Novel Phenomena of 

 Alternating Currents," may be seen an account of some experiments 

 by Professor Elihu Thomson on the mechanical force between con- 

 ductors in which alternating currents are circulating. 



In the case of a ring of metal in the presence of an electromagnet, 

 in the coils of which an alternating current is passing, a force of 

 repulsion is experienced by the ring, which may be explained as 

 follows : 



Were the induced currents in the closed conductor unaffected by 

 self-induction, the only phenomena exhibited would be alternate equal 

 attractions and repulsions. 



This may be illustrated by fig. 1. Here the strong line represents 

 the primary and the thin the secondary, while of the dotted line any 



