f 101 4 
XIII. Further Considerations on the Doctrine that the Pha- 
nomena of Terrestrial Gravitation are occasioned by known 
Terrestrial Motions. By Sir RicuarD PHILLIPS. 
To Mr. Tilloch. 
Sir, — Sixcr the publication of the theory which resolves the 
phenomena of weight, and of falling bodies, into the orbicular and 
rotary motions of the earth, objections have been started, by va- 
rious persons in conversation, and through the public press 
which the author’s love of truth, and his respect for some of 
the parties, induce him to consider. 
I. It has been doubted whether bodies would fall in the exv- 
hausted receiver of an air-pump upon this hypothesis. 
To this it may be replied, that the exhausted receiver, the 
contained vacuum, and the bodies let fall before, and at the in- 
‘stant of fall, are all of them as much the patients of the orbicular 
and rotary motions, as though no such exhaustion had taken 
place. The orbicular motion was carrying forward the whole, 
and the rotary motion was endeavouring to deflect every part of 
the sustained mass, from the right line of the orbicular motion. 
The difference arising from the absence of the air is the same, 
whatever might be the source of the power which caused the 
bodies to fall; that is, a feather would fall in the same time as 
a guinea, simply because the atmosphere epposed no resistance, 
whether the centripetal force was produced by governing mo- 
tions or by attraction. 
Il. It is objected that a projectile would continue to ascend 
Sor ever, unless ihe force uf attraction drew it towards the earth, 
To this I reply, that the deflective force of the rotary motion 
is equivalent, in the retardation of a projectile, to the supposed 
attraction; and that, in combination with the resistance of the 
atmosphere, that deflective force produces all the phenomena 
of projectiles, being the orbicular force common to both hypo- 
theses. 
Ill. It has been objected that, if a body were let fall in the 
atmosphere, it would either go off in a tangent into space, or 
would move for ever in that place, but for the earth’ s attraction. 
In regard to the assertion, that it might move off in a tan- 
gent, it need only be considered, that no force has been given it 
in the direction of such tangent, and that bodies do not move 
in any required direction without some force exerted in that di- 
rection. 
And that it will not move for ever in an unsupported spot in 
the atmosphere, arises from the influence of the deflecting rotary 
motion, of which it partook when placed there, in which it con- 
tinues, and which it also derives from the surrounding medium, 
G3 Iv i 
