Galilei, Galileo Dialogues on two world systems 1661, tr. Salusbury, Thomas

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343
understood what those mutations are, and amongst what stars
they should be discerned; therefore it would be necessary that
we in the next place narrowly examine this particular. My ha­

ving onely found written in general terms that the annual moti­
on of the Earth about the Grand Orb, ought not to be admit­
ted, because it is not probable but that by means of the same
there would be discoverd some apparent mutation in the fixed
stars, and not hearing say what those apparent mutations ought to
be in particular, and in what stars, maketh me very reasonably
to infer that they who rely upon that general position, have not
understood, no nor possibly endeavoured to understand, how
the businesse of these mutations goeth, nor what things those
are which they say ought to be seen. And to this judgment I am

the rather induced, knowing that the annual motion ascribed
by Copernicus to the Earth, if it should appear sensible in the
Starry Sphere, is not to make apparent mutations equal in re­
spect to all the stars, but those appearances ought to be made
in some greater, in others lesser, and in others yet lesser; and
lastly, in others absolutely nothing at all, by reason of the
vast magnitude that the circle of this annual motion is supposed
to be of. As for the mutations that should b seen, they are of
two kinds, one is the said stars changing apparent magnitude,
and the other their variation of altitudes in the Meridian. Upon
which necessarily followeth the mutation of risings and settings,
and of their distances from the Zenith, &c.

Enquiry is made
what mutations, &
in what stars, are to
be discovered, by
means of the an­
nual motion of the
Earth.

Astronomers ha­
ving omitted to in­
stance what alte­
rations those are
that may be deri­
ved from the an­
nual motion of the
Earth, do thereby
testifie that they
never rightly un­
derstood the same.

The mutations
of the fixed stars
ought to be in some
greater, in others
lesser, and in others
nothing at all.

SAGR. Methinks I see preparing for me such a skean of these
revolutions, that I wish it may never be my task to dis-intangle
them, for to confesse my infirmity to Salviatus, I have some­
times thought thereon, but could never find the ^{*} Lay-band of

it, and I speak not so much of this which pertains to the fixed
stars, as of another more terrible labour which you bring to my
remembrance by maintaining these Meridian Altitudes, Ortive
Latitudes and distances from the Vertex, &c. And that which

puzzleth my brains, ariseth from what I am now about to tell
you. Copernicus supposeth the Starry Sphere immoveable, and
the Sun in the centre thereof immoveable also. Therefore eve­
ry mutation which seemeth unto us to be made in the Sun or in
the fixed stars, must of necessity befall the Earth and be ous.
But the Sun riseth and declineth in our Meridian by a very great
arch of almost 47. degrees, and by arches yet greater and
greatet, varieth its Ortive and Occidual Latitudes in the oblique

Horizons. Now how can the Earth ever incline and elevate so
notably to the Sun, and nothing at all to the fixed stars, or so
little, that it is not to be perceived? This is that knot which
could never get thorow my ^{*} Loom-Combe; and if you shall