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fixed stars are used in determining those of the planets. ^ ie }'have many things in common. Both are subject to the inequa-lities of refraction, aberration, precession and nutation. But,without going far into the circumstances of distinction betweenthe fixed stars and the planets, it is obvious that there must bepeculiarities belonging to the latter from their relative proximityto the observer, and their continual change of place. The formercircumstance renders them subject to parallax, and the latter (j°mention one instance) modifies the quantity of aberration : f° r <the time of the transmission of light from the planet to the Eartn,the former has changed its place.

But these are only slight circumstances of distinction. lplanets’ distances, velocities, the forms of their orbits must b einvestigated : subjects of enquiry to which there is nothing lik e 1Dthe preceding discussions, and depending on principles not y etlaid down. Our attention will be directed to these points insucceeding part of this Volume : and as, amongst the plan®* 9 'the Earth claims the chief consideration, its theory shall b efirst discussed.

END OF THE FIRST PART OF THE FIRST VOLUME.