B, that all the fixed
stars are precisely of the same _magnitude_; in which case, every
variety in the size will indicate a corresponding difference in the
distance, and will measure that difference. Nor could we imagine any
exception to these inferences from A or from B, whichever of the two
were assumed, unless through optical laws that might not equally affect
objects under different circumstances; I mean, for instance, that might
suffer a disturbance as applied under hypoth. B, to different depths in
space, or under hypoth. A, to different arrangements of structure in
the star. But thirdly, it is certain, that neither A nor B is the
abiding law: and next it becomes an object by science and by
instruments to distinguish more readily and more certainly between the
cases where the distance has degraded the size, and the cases where the
size being _really_ less, has caused an exaggeration of the
distance: or again, where the size being really less, yet co-operating
with a distance really greater, may degrade the estimate, (though
travelling in a right direction,) below the truth; or again where the
size being really less, yet counteracted by a distance also less, may
equally disturb the truth of human measurements, and so on.
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