172 TRANSACTIONS OF SCIENTIFIC SECTION. 
quently, could have no effect in producing either of the 
Stoppages. 
To prove that when nutation ceases, precession ceases, 
ITuse the same apparatus and set the wheel in motion as 
before. Precession, as you see, begins at once. Now I 
pull upward by means of a cord on the free end of my 
gyroscope, just enough to stop the tilting downward. 
Instantly the precessional movement ceases. I slacken 
the string, it begins again. I pull upwards, and again it 
stops. Vary itas I may, when there is nutation, there 
is precession, and at no other time. 
It is impossible to get the precession without the nu- 
tation, but it is easy to make the machine tilt up, or 
down, without the precession. When I pulled the 
string horizontally, there was no precession, but the wheel 
tilted down. Or if the wheel does not revolve on its 
own axis, gravity will readily cause it to tilt, but no 
lateral movement will occur. If the lever is overlcaded 
so that that end is the heavier, the results are the same. 
From these experiments we must conclude that nuta- 
tion (or tilting) and precession are not mutually inde- 
pendent, and since precession is alwaysa function of nu- 
tation and the rate of axial rotation, varying directly as 
the former and inversely as the latter, and since nuta- 
tion is, at least sometimes, independent of both, we may 
reasonably regard nutation (or tilting) as the cause, and 
precession as the effect. This is true of the earth as 
weli as of the gyroscope. 
The following gentlemen were unanimously elected 
members of the Scientific Section, viz.: Silas Wodell, J. 
B. T. Tuthill, and Theodore Neumann. 
Mr. Winne nominated for membership Mr. George B. 
Rogers. 
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