1880.] 



On an Electro-Magnetic Gyroscope. 



305 



II. " On an Electro-Magnetic Gyroscope." By M. Wilfrid de 

 Fonyielle- Communicated by the President. Received 

 April 15, 1880. 



I have the honour to submit to the Royal Society of London an 

 apparatus which I have invented, after having witnessed an experi- 

 ment by M 4 Dieudonne Lontin. 



The original Lontin experiment consists in the rapid and continuous 

 rotation of a magnetised steel needle, placed under the influence of 

 the currents of a peculiar induction machine. 



The object of my apparatus is to give a movement of rotation in a 

 horizontal plane, not only to a needle, but to any moveable piece of 

 iron which is symmetrical in reference to its axis of rotation. It is 

 consequently composed of (1) a vertical coil, which I have made rec- 

 tangular, but is susceptible of receiving any form ; (2) a Ruhmkorff 

 coil of a peculiar construction ; and (3) the axis of suspension. This 

 piece can be removed at pleasure, and another substituted, thus 

 demonstrating the form to be indifferent, if it is placed in equilibrium. 

 The coil may however be horizontal, and in that case the moveable 

 piece will rotate in a vertical plane. 



The apparatus has been constructed in order to work easily with 

 one Bunsen cell of 20 centims. height, or with one or two bichromate 

 of potassium cells. 



Above the frame is placed a horseshoe-magnet, supported by a 

 vertical axis, round which it can be placed in any particular azimuth 

 that may be required for the experiments. This axis can be taken 

 away, and the horseshoe-magnet can be replaced by one or two or a 

 large number of bar-magnets, laid flat upon the frame. It is possible 

 also to place other bar-magnets underneath the frame, in a space 

 arranged for this purpose. It is possible also to place four magnets 

 laterally, two on each side of the frame, or to replace them by a 

 number of electro-magnets. 



To produce a continuous movement of rotation, the magnets do not 

 appear to be absolutely necessary, although they greatly increase the 

 velocity, and outweigh every chance of perturbation and uncertainty. 



But the motion without magnets presents peculiarities, which are of 

 great interest, and have led to an explanation, accepted by M. Lontin, 

 and which will be developed more fully hereafter. 



Under ordinary circumstances the moveable piece does not start by 

 itself, but requires an external impulse. 



Another peculiarity of this movement is that the direction of the 

 current can be altered without altering, in any respect, the direction of 

 the rotation, although sometimes it diminishes or increases the velocity. 

 But owing to the necessity of giving an impulse to the moveable 



