180 ANNUAL OP SCIENTIFIC DISCOVERT. 



it into rapid rotatory motion, and handing it round the room, each person 

 that held it found himself forcibly resisted in any attempt to turn it round 

 either in his fingers, to the right hand or left, or up or down, or in his 

 hands if he swung it round. So that the idea was irresistibly suggested 

 to the mind, that there was something living within which had a will of 

 its own, and which always opposed your will to change its position. The 

 second modification presented the mass suspended in a stout ring, which 

 was furnished with projecting axles, like the ring of the gymbal. These 

 axles could be placed in a small frame of wood bushed with brass. This 

 small frame, when placed on a piece of smooth board, could be turned 

 freely round by turning the piece of board on which it rested as long as 

 the gyroscope was not revolving, friction being sufficient to cause the one 

 to turn with the other ; but, when the gyroscope was set rapidly revolving, 

 in vain you attempted to turn the frame by turning the board on which 

 it rested, so determinately did it endeavor to maintain its own plane of rota- 

 tion as quite to overpower the friction. In the third modification of the 

 g3 r roscope it was suspended in gymbals, so exquisitely constructed that both 

 the gyroscope proper and the supporting gymbals were accurately balanced, 

 so as to rest freely when placed in any position in relation to the earth. 

 By this the author showed most strikingly the effect of any attempt to 

 communicate revolving motion round any other axis to a mass already 

 revolving ; for, on placing the gymbals in a frame of wood while the gyro- 

 scope was not revolving, it remained quite steady ; but, when thrown into 

 rapid revolving motion, the slightest attempt to turn the frame round to 

 the right or to the left was instantly followed by the entire gyroscope 

 turning round in the gymbals, so as to bring its axis to coincide with the 

 new axis you endeavored to give it with a life-like precision, and always 

 so as to make its own direction of revolution be the same as that of the 

 slightest turn you impart to it. Having thus demonstrated the necessary 

 effect of combining one rotatary motion with another, he then proceeded to 

 demonstrate palpably that the earth's revolving motion affected the gyro- 

 scope in precisely a similar way. Having, by the screw adjustments, 

 brought the gyroscope, in gymbals, to a very exact balance, it remained 

 fixed in any position when not revolving. But, rapid rotatory motion 

 having been communicated to the gyroscope mass as soon as the gymbal 

 supports are placed on the stand, you see the entire apparatus, slowly at 

 first, but at length more rapidly, turn itself round, nor ever settle until 

 the axis, on which the gyroscope is revolving, arranges itself parallel-to the 

 terrestrial axis, in such a sense as to make the direction of the revolving 

 gyroscope be the same as that of the whole earth. He next showed that 

 the determination with which it did this was sufficient to control the entire 

 weight of the instrument, though that amounted to several pounds ; for, 

 taking the ring gyroscope from the side of the ring of which a small steel 

 wire projected, ending in a hook, the wire coincided with the prolonga- 

 tion of the axis of the gyroscope : of course, when not made to revolve, 

 the hook, if placed in a little agate cup at the top of a stand, would permit 

 the instrument, by its weight, to fall instantly, as soon as the support of 



