Arago urged Le Verrier
to undertake the great problem of searching for this body, whose
theoretical existence seemed demonstrated. But the conditions of the
search were such that it must needs be conducted on principles wholly
different from any search which had ever before been undertaken for a
celestial object. For this was not a case in which mere survey with
a telescope might be expected to lead to the discovery.
Certain facts might be immediately presumed with reference to the
unknown object. There could be no doubt that the unknown disturber
of Uranus must be a large body with a mass far exceeding that of the
earth. It was certain, however, that it must be so distant that it
could only appear from our point of view as a very small object.
Uranus itself lay beyond the range, or almost beyond the range, of
unassisted vision. It could be shown that the planet by which the
disturbance was produced revolved in an orbit which must lie outside
that of Uranus. It seemed thus certain that the planet could not be
a body visible to the unaided eye. Indeed, had it been at all
conspicuous its planetary character would doubtless have been
detected ages ago. The unknown body must therefore be a planet which
would have to be sought for by telescopic aid.
Pages:
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378