404 Mr. W. Ladd on a Magneto -electric Machine. [March 14^ 



second impulse. The current in this shunt wiU be found to travel in alter- 

 nate directions ; not so that on the electromagnet. 



When the armature is discharging its current into the electromagnets, 

 the current in the shunt is in the direction it would have if the shunt 

 were in circuit solely with the armature. 



When the armature is changing poles and is disconnected, the secondary- 

 current is in full play, and the current in the shunt is in the direction of 

 the current prolonged in the electromagnet, that is, of the extra current. 



The force expended in the shunt is wasted in heat ; but a secondary wire 

 on the electromagnet or a copper cylinder would very greatly add to the 

 power by maintaining the magnetism, and not consume uselessly the force 

 now wasted in the shunt. 



The overlapping of the armature and the solid mass of the electromag- 

 nets tends to maintain imperfectly the magnetism during the intervals of 

 no current from the armature ; and but for this the machines, whether they 

 be Wilde's, Wheatstone's, or Siemens' s, would none of them work. 



In 1860 I published a description of two machines I had constructed, 

 and in 1862, at the Universal Exhibition, I exhibited a machine for adding 

 mechanical force to static electricity without friction. A machine similar 

 in principle, but a little diiferent in construction, has been exhibited recently 

 under the name of Holtz. 



One of my machines bears to the other precisely the same relation that 

 Siemens' s or Wheatstone's does to "Wilde's. 



If these be of sufficient interest to the Royal Society, I shall be happy 

 to exhibit them. 



I am, my dear Sir, 



Very truly yours, 



C. F. Yarley. 



IV. "On a Magneto-electric Machine.'^ By William Ladd, 

 F.U.M.S. Communicated by Professor Stokes, Sec. R.S. 

 Received March 14, 1867. 



In June 1864 I received from Mr. Wilde a small magneto-electric ma- 

 chine, consisting of a Siemens' s armature and six magnets. This I endea- 

 voured to improve upon, my object being to get a cheap machine for blast- 

 ing with Abel's fusees. This was done by making one of circular magnets, 

 and a Siemens' s armature revolving directly between the poles, the arma- 

 ture forming the circles ; with this I could send a very considerable power 

 into an electro-magnet, &c. It was then suggested to me by my assistant, 

 that if the armature had two wires instead of one, the current from one 

 being sent through a wire surrounding the magnets, their power would be 

 augmented, and a considerable current might be obtained from the other 

 wire available for external work ; or there might be two armatures, one to 



