■ 332 Mr. Landen’s Invejiigatwn , &c. 
other bodies in our fyftem) ; it follows ; that it will not conti- 
nually revolve about either of thofe axes, but will revolve, or 
endeavour to revolve, about fucceffive momentary axes, as (hewn 
above. If then its three permanent axes of rotation be called 
its firjl, Jecond , and third axes ; and the poles of its frfi axis be 
thofe about which its momentary poles are. carried according to 
our theory ; the Jecond and third axes will be in the plane of its 
equator, the three being at right angles to each, other. There- 
fore, with refpedl to the above theory, this terreftrial mafs mu ft 
be confidered of fuch a form, that its equator, and any feftion 
parallel thereto, fnall rather be elliptical than circular. And, 
denoting its firft, fecond, and third axes by b, c , d , refpedlively, 
obfervations evince, that the difference c - b will be much 
greater than the difference d - c. Whence it follows, that (fup- 
poiing the earth’s rotatory motion to be difturbed only by the. 
centrifugal force arifing from the inertia of its own particles) the 
track of polar evagation with us will be nearly circular, and the 
radius of the limiting circle very fmall, whether we have regard 
to the moveable or immoveable fpherical furface referred to 
above ; but that, in the latter furface, fuch circle will be much 
lefs than in the former : and it moreover follows, that the con- 
cavity of the track upon the moveable furface will continually 
touch and roll along the convexity of the track in the immove- 
able furface. 
In other planets, the tracks of polar evagation may, from a 
iimilar caufe, be very different. The theory above explained 
evidently proves, that their axes of rotation may poffibly vary 
greatly in portion, merely through the inertia of mattery whilft 
Providence has fo ordered it, that the pofition of the axes of 
rotation of this planet fhall, by that caufe, be but . very little 
altered. 
