C. B. WARRING. L93 



If I understand Mr. Forbes aright, he means that no 

 possible movement in the ether can cause the shell to 

 revolve on its axis. It may blow east or west, north or 

 south, up or down, or in any intermediate direction, 

 and will carry the shell with it, but there will be no ten- 

 dency to rotation ; and this doubtless is true. And, fur- 

 thermore, that a gyrostatic effect will be produced in 

 every case, except when the molecule is accelerated 

 along its axis. 



This last statement shows a strange ignorance of the 

 cause of gyrostatic effects. It has been shown that there 

 can be no such effects without (1) the rotation of the 

 gyroscopic body on its axis, and (2) another force tend- 

 ing to make the body revolve around a second axis inter- 

 secting the first at right angles. Futhermore, it has 

 been shown that in every case of gyrostatic effect the 

 first axis changes its direction. So long, therefore, as 

 the axis remains parallel to itself, which will be forever, 

 unless some force other than the ether acts upon it, the 

 ether may drift the molecule not only along its axis, 

 but in any other conceivable direction, and in no case 

 will any gyrostatic effects be produced. 



Experimental proof : set a gyroscope in action ; move 

 it in any direction, keeping the axis parallel to itself, 

 there is no resistance and no gyration. Again : set a 

 Bohnenbergher in rotation ; place it so that its axis is 

 parallel to that of the earth. It is moving in space with 

 enormous velocity, and not ''along its axis,'' yet no 

 gyrostatic effect is produced. 



For there can be no gyrative effect without the simul- 

 taneous existence of rotation on one axis, and of a force 

 tending to produce rotation on a second axis, perpen- 

 dicular to the first. If there is, as in case of Mr. 

 Forbes' s molecule, only the rotation on an axis, and a 

 motion of translation, the second indispensable element 

 is wanting. 



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