142 !Mr. E. Huxt on certain Phenomena connected with 



forces being thus inclined to the wheel, tend to turn it round, so as to 

 cany the end a of the spindle towards c, and the part F towards k. 

 But the part f cannot move from the point of support, so that the 

 reaction of the pressure towards k, along with the pressure on the end 

 A, towards c, will tend to turn the wheel about the centre F, so as to 

 bring its spindle F a to coincide with the line c c. In other words, the 

 moment round the centre, F, resulting from the centrifugal forces on 

 opposite sides of the wheel, carries the wheel round towards c. Beyond 

 this point the explanation is identical with that already given of the 

 action of the Bohnenberger apparatus. My adjustable apparatus can 

 be arranged to show the transformation from the Bohnenberger to a 

 modification of the Fessel apparatus, whilst in motion ; the fly-wheel 

 performing a portion of a precessional revolution about its own centre, 

 and then moving round a centre at a short distance on one side. 



I must now remind you that so far we have only considered cases in 

 which the spindle of the gyroscope is in a horizontal position, the weight 

 tending to turn it about another axis which is also horizontal. The 

 resultant axis being in the same plane, the precessional motion is conse- 

 quently in the horizontal plane. If, however, the spindle is, at starting, 

 at all inclined to the horizon, the plane in which the two axes lie, will, 

 of course, be inclined also, and the spindle will therefore teml to move 

 in that inclined plane. Let A f, figs. 10 and 11, represent the inclined 

 spindle, fig. 10 being an elevation, and fig. 11 a plan. The weight 

 applied at a will tend to turn the wheel about the hoiizontal line l ir, 

 and LAM will be the plane passing through the two axes. The spindle 

 a f will therefore tend to move towards c F, in the plane l a m ; but 

 the weight moves with the end A of the spindle, and as the action of 

 the weight is continuous, no movement, however small, of the spindle, 

 can take place towards cf, without altering the position of the horizontal 

 line L 31, about which the weight tends to turn the wheel. As the 

 spindle A F moves towards c f, the imaginary axis, i M, moves towards 

 o p, fig. 11, and the plane through the two axes consequently continually 

 moves round. The result is, that the spindle a f actually moves on the 

 surface of a cone, of which the vertical line N f, fig. 10, is the axis, 

 whilst the end A of the spindle, carrying the weight, moves in the 

 horizontal circle, A c K, forming the base of the cone. The weight is 

 therefore carried round horizontally, whether the spindle of the gyro- 

 scope is at stai-ting in a horizontal or in an inclined position. 



The gyroscope does not in all cases present a complete example of 

 the phenomena I have explained, and the action is generally very much 

 modified by friction and by the resistance of the air. One way in which 

 friction brings down the weight has alreadv been alluded to : the resist- 



