Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/176

 likewise moveth with like velocity, nor doth it depart from rest, but from a motion equal to that of the Earth, wherewith it intermixeth the supervenient motion of descent, and of those two composeth a third which is transversal or side-ways.

But for Gods sake, if it move transversly, how is it that I behold it to move directly and perpendicularly? This is no better than the denial of manifest sense; and if we may not believe sense, at what other door shall we enter into disquisitions of Philosophy?

In respect to the Earth, to the Tower, and to our selves, which all as one piece move with the diurnal motion together with the stone, the diurnal motion is as if it never had been, and becometh insensible, imperceptible, and without any action at all; and the onely motion which we can perceive, is that of which we partake not, that is the descent gliding along the side of the Tower: You are not the first that hath felt great repugnance in apprehending this non-operating of motion upon things to which it is common.

Now I do remember a certain conceipt, that came one day into my fancy, whilst I sailed in my voyage to Aleppo, whither I went Consul for our Countrey, and possibly it may be of some use, for explaining this nullity of operation of common motion, and being as if it never were to all the partakers thereof. And if it stand with the good liking of Simplicius, I will reason with him upon that which then I thought of by my self alone.

The novelty of the things which I hear, makes me not so much a patient, as a greedy and curious auditor: therefore go on.

If the neb of a writing pen, that I carried along with me in the ship, through all my navigation from Venice to * Scanderon, had had a facultie of leaving visible marks of its whole voyage, what signs, what marks, what lines would it have left?

It would have left a line distended from Venice thither, not perfectly streight, or to say better, distended in a perfect arch of a circle, but in some places more, in some less curved, according as the vessel had gone more or less fluctuating; but this its inflecting in some places a fathom or two to the right hand or to the left, upwards or downwards, in a length of many hundred miles, would have brought but little alteration to the intire tract of the line, so that it would have been hardly sensible; and without any considerable error, might have been called the part of a perfect arch.

So that the true and most exact motion of the neb of my pen would have also been an arch of a perfect circle, if the vessels motion, the fluctuation of the billows ceasing, had been