Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/369

 gresse I make is not in plano, but about the circumference of the Terrestrial Globe, which at every step changeth inclination in respect to Heaven, and consequently maketh the same change in the Instrument which is erected upon the same.

You say very well: And you know withal, that by how much the bigger that circle shall be upon which you move, so many more miles you are to walk, to make the said star to rise that same degree higher; and that finally if the motion towards the star should be in a right line, you ought to move yet farther, than if it were about the circumference of never so great a circle?

True: For in short the circumference of an infinite circle, and a right line are the same thing.

But this I do not understand, nor as I believe, doth Simplicius apprehend the same; and it must needs be concealed from us under some mistery, for we know that Salviatus never speaks at random, nor proposeth any Paradox, which doth not break forth into some conceit, not trivial in the least. Therefore in due time and place I will put you in mind to demonstrate this, that the right line is the same with the circumference of an infinite circle, but at present I am unwilling that we should interrupt the discourse in hand. Returning then to the case, I propose to the consideration of Simplicius, how the accession and recession that the Earth makes from the said fixed star which is neer the Pole can be made as it were by a right line, for such is the Diameter of the Grand Orb, so that the attempting to regulate the elevation and depression of the Polar star by the motion along the said Diameter, as if it were by the motion about the little circle of the Earth, is a great argument of but little judgment.

But we continue still unsatisfied, in regard that the said small mutation that should be therein, would not be discerned; and if this be null, then must the annual motion about the Grand Orb ascribed to the Earth, be null also.

Here now I give Salviatus leave to go on, who as I believe will not overpasse the elevation and depression of the Polar star or any other of those that are fixed as null, although not discovered by any one, and affirmed by Copernicus himself to be, I will not say null, but unobservable by reason of its minuity.

I have already said above, that I do not think that any one did ever set himself to observe, whether in different times of the year there is any mutation to be seen in the fixed stars, that may have a dependance on the annual motion of the Earth, and added withal, that I doubted least haply some might never have