0. B. WARRING. 105 



ized, or which are entitled to consideration on account 

 of the eminence of their authors. 



One of the most common of these erroneous notions 

 is that there is an inherent power of resistance in the 

 rapidly rotating wheel. It will, however, be found on 

 trial that the slightest force is enough to turn the wheel 

 out of its plane of rotation, no matter how fast it re- 

 volves. A gyroscope, supported as in fig. 3 (where the 

 two cords are knotted at a, so as to rjrevent slipping), 

 will turn in azimuth without any sensible resistance ; even 

 the torsion of a thread will suffice to turn it. 



There are several other modes of showing this lack 

 of "inherent resisting power." Two of them will be 

 pointed out hereafter ; one when discussing the so-called 

 gyrostatic compass, and the other in the part of my 

 paper which treats of the gyroscopic pendulum. 



Another erroneous explanation is found in Appletort s 

 Cyclopedia — "Gyroscope." We are there told that the 

 horizontal movement of this curious instrument is due 

 to gravity acting with the rotary motion on the descend- 

 ing side, and against it on the other, thus producing an 

 excess of force on one-half of the wheel, which pushes 

 it towards the weaker side. 



To show how wrong this is, pass the standard in fig. 1 

 through a small hole in the lug until stopped by a ring a 

 little below the point. Evidently, the instrument has 

 freedom to move in a horizontal plane, but not to go 

 downward. Now, set the wheel in rapid motion. It 

 makes no effort to go to the right or to the left ; yet 

 gravity is all the time acting with the descending side 

 and against the ascending one. 



The same thing can be proved in many other ways, all 

 giving the same result. 



The most noted discussion of the gyroscope is that by 

 General Barnard. His article, with its two supplements, 

 is devoted to the higher mathematics of the subject, and, 



89 



