TRANSACTIONS OF THE SECTIONS. 27 



A Magnetic Paradox. By S. Alfred Vablet, Assoc. Inst. C.E. 

 The author stated that the instrument which had been called a magnetic paradox 

 (because the phenomenon it presented was the apparent repulsion of iron by a mag- 

 net) consisted of a compound magnet in a box, and when pieces of iron were placed 

 over the poles on the box they became magnetic by induction, and were attracted 

 by the magnet ; but if a bar of soft iron, not in itself magnetic, were approached 

 near to the pieces of iron, the pieces of iron leap away from the box and become 

 attached to the soft iron bar. The effect produced was stated to be due to the fact 

 that mametic force was transmitted by induction; when the soft iron bar was ap- 

 proached to the pieces of iron, the magnetic forces resident in them, which had been 

 separated and rendered active by the magnet on the box, developed the magnetic 

 forces resident in the soft iron bar, and consequently it followed (the resistance 

 which soft iron opposes to magnetic polarization being so small that it may be here 

 disregarded) that as the dual forces resident in iron are equal (and the one force 

 cannot be called into being without equally developing the other) when the bar is 

 approached nearer to the pieces of iron than the poles of the magnet, they are at- 

 tracted away from the box by the superior attraction exerted by the soft iron bar. 

 It was shown that when pieces of iron were placed direct upon the poles of the 

 magnet, they could be removed by the superior atti-action of the soft iron bar over 

 that of the magnet ; the explanation of this effect was stated to be the iron bar 

 collected the lines of magnetic force issuing from the magnets, and the magnetism 

 developed in the iron bar was more localized than in the magnetized bars compo- 

 sino; the mamet in the box. 



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A Description of the Electric Time-Signed eit Port Elizaheth, Cape of Good 



Hope. Bg S. Alfred Varley, Assoc. Inst. C.E. 

 The author having described the general ai-rangements connected with the Liver- 

 pool time-ball, of which he had the charge at the time of its erection, the methods 

 he adopted for measuring the time which elapsed between the current leaving 

 Green\\ach and the falling of the ball at Liverpool, and the means employed for 

 checking the working the apparatus in the telegraph offices, he stated the time which 

 elapsed between the arrival of the time-current in London and the falling of the 

 ball at Liverpool was ij- of a second ; /„• of this interval of time was occupied 

 by the electric current travelling through an underground circuit from London 

 to Liverpool, and -^^ in discharging the apparatus at London and Liverpool. In 1859, 

 Sir Thomas Maclear, the Astronomer Royal at the Cape of Good Hope, inspected 

 the electrical time-signals in this country, with a view of erecting time-balls in 

 connexion with the Royal Observatory at Cape Town, and this led the author 

 afterwards to design at different times two time-triggers for use in the Cape. In 

 September 1864'the author was requested to construct a trigger for discharging a 

 time-ball to be erected at Port Elizabeth ; and as he considered the intervention of 

 any relay or secondary apparatus to be objectionable, he determined, if possible, to 

 construct the trigger sensitive enough to be discharged by the batteries in the Cape 

 Town Observatoiy ; and in its construction he adopted a modification of a principle 

 first introduced by Professor Hughes in his printing telegi-aph _ (described at the 

 Newcastle Meeting). The trigger was constructed with a soft iron armature ren- 

 dered magnetic by induction from a compound bar magnet, and the armature 

 strongly attracted the soft iron cores of an electromagnet, but was prevented fi-om 

 actually touching the poles of the electromagnet. A spiral spring attached to this 

 armature was so adjusted that it neai-ly overcame the magnetic attraction induced 

 by the bar magnet. The time-current polarized the electromagnet in the opposite 

 direction to that induced by the bar magnets ; and as the attraction between the 

 armature and the soft iron cores was already almost overcome by the spiral spring, 

 a very small amoimt of polarization in the opposite direction was necessary to re- 

 lease the armatm-e which was rapidly pulled away by the spring, and the trigger 

 discharged. The rapidity of discharge with this trigger was very great ; j'o W^ °^ 

 a second only elapsed between the arrival of the time-cuiTent and the falling of the 

 ball. From a report in the Port Elizabeth paper of August 29, 1S65, giving an 

 account of the inaugui'ation of this time-signal, and forwarded to the author by 



