Simpl.You believe then, that two stones, or two pieces of Iron taken at chance, and put together, do for the most part touch in one sole point?
Salv.In casual encounters, I do not think they do; as well because for the most part there will be some small yielding filth upon them, as because that no diligence is used in applying them without striking one another; and every small matter sufficeth to make the one superficies yield somewhat to the other; so that they interchangeably, at least in some small particle, receive figure from the impression of each other. But in case their superficies were very terse and polite, and that they were both laid upon a table, that so one might not presse upon the other, and gently put towards one another, I question not, but that they might be brought to the simple contact in one onely point.
Sagr.It is requisite, with your permission, that I propound a certain scruple of mine, which came into my minde, whil'st I heard proposed by Simplicius, the impossibility of finding a materiall and solid body, that is, perfectly of a Spherical figure, and whil'st I saw Salviatus in a certain manner, not gainsaying, to give his consent thereto; therefore I would know, whether there would be the same difficulty in forming a solid of some other figure, that is, to expresse my self better, whether there is more difficulty in reducing a piece of Marble into the figure of a perfect Sphere, than into a perfect Pyramid, or into a perfect Horse, or into a perfect Grasse-hopper?
Salv.To this I will make you the first answer: and in the first place, I will acquit my self of the assent which you think I gave to Simplicius, which was only for a time; for I had it also in my thoughts, before I intended to enter upon any other matter, to speak that, which, it may be, is the same, or very like to that which you are about to say;The Sphericall Figure is easier to be made than any other. And answering to your first question, I say, that if any figure can be given to a Solid, the Spherical is the easiest of all others, as it is likewise the most simple, and holdeth the same place amongst solid figures,The circular Figure only is placed amongst the postulata of Mathematicians. as the Circle holdeth amongst the superficial. The description of which Circle, as being more easie than all the rest, hath alone been judged by Mathematicians worthy to be put amongst the ** Demands or Petitions. postulata belonging to the description of all other figures. And the formation of the Sphere is so very easie, that if in a plain plate of hard metal you take an empty or hollow circle, within which any Solid goeth casually revolving that was before but grosly rounded, it shall, without any other artifice be reduced to a Spherical figure, as perfect as is possible for it to be; provided, that that same Solid be not lesse than the Sphere that would passe thorow that Circle. And that which is yet more worthy of our consideration is, that within the self-sameincavity
