Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/185

 with that which hath been said already, namely, that in case the Earth should move, the shots made Eastward would prove too high, &c. the ball, as it is probable, being to move along the tangent.

But if I should say, that so it falleth out upon triall, how would you censure me?

It is necessary to proceed to experiments for the proving of it.

But do you think, that there is to be found a Gunner so skilful, as to hit the mark at every shoot, in a distance of v.g. five hundred paces?

No Sir; nay I believe that there is no one, how good a marks-man soever that would promise to come within a pace of the mark,

How can we then, with shots so uncertain, assure our selves of that which is in dispute?

We may be assured thereof two wayes; one, by making many shots; the other, because in respect of the great velocity of the Earths motion, the deviation from the mark would in my opinion be very great.

Very great, that is more than one pace; in regard that the varying so much, yea and more, is granted to happen ordinarily even in the Earths mobility.

I verily believe the variation from the mark would be more than so.

Now I desire that for our satisfaction we do make thus in grosse a slight calculation, if you consent thereto, which will stand us in stead likewise (if the computation succeed as I expect) for a warning how we do in other occurrences suffer our selves, as the saying is, to be taken with the enemies shouts, and surrender up our belief to what ever first presents it self to our fancy. And now to give all advantages to the Peripateticks and Tychonicks, let us suppose our selves to be under the Equinoctial, there to shoot a piece of Ordinance point blank Eastwards at a mark five hundred paces off. First, let us see thus (as I said) in a level, what time the shot after it is gone out of the Piece taketh to arrive at the mark; which we know to be very little, and is certainly no more than that wherein a travailer walketh two steps, which also is less than the second of a minute of an hour; for supposing that the travailer walketh three miles in an hour, which are nine thousand paces, being that an hour containes three thousand, six hundred second minutes, the travailer walketh two steps and an half in a second, a second therefore is more than the time of the balls motion. And for that the diurnal revolution is twenty four hours, the Western horizon riseth fifteen degrees in an hour, that