235 
Motion of the Sun, and solar System. 
to admit, if the sun were at rest ; and, to remove this objection, 
the necessity for admitting its motion ought to be well 
established. 
Theoretical Considerations. 
A view of the motion of the moons, or secondary planets, 
round their primary ones, and of these again round the sun, 
may suggest the idea of an additional motion of the latter 
round some other unknown center ; and those who like to 
indulge in fanciful reviews of the heavens, might easily 
build a system upon hypotheses not altogether without some 
plausibility in their favour. Accordingly we find that Mr. 
Lambert, in a work which is full of the most fantastic imagi- 
nations, has framed a system wherein the sun is supposed to 
move about the nebula in Orion.* But, setting aside the extra- 
vagant idea of making this luminous spot a center of motion, 
it must certainly be admitted that the solar motion itself is at 
least a very possible event. 
I have already mentioned, in a note to my former Paper,' f 
that the possibility of a solar motion has also been shown from 
theoretical principles by the late Dr. Wilson of Glasgow ; and 
its probability afterwards, from reasons of the same nature, by 
Mr. De la Lande. The rotatory motion of the sun, from 
which he concludes a displacing of the solar center, must cer- 
tainly be allowed to indicate a motion of translation in space ; 
for though it may be possible, it does not appear probable, that 
any mechanical impression should have given the former, 
without occasioning the latter. But, as we are intirely unac- 
quainted with the cause of the rotatory motion, the solar 
* See Systeme du Monde de Mr. Lambert, page 152, and 158. 
| See Phil. Trans, for the year 1783, page 283. 
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