. . . . Which words are neither cautelous, nor subterfugious, but are as downe right in their plainnesse, as they are touching, and pernitious, by two much derogating from many, and glancing upon many noble personages, with too grosse, if not too base an attribute, in tearming them doers of tricks, as it were to iuggle: because they perhaps make use of a necessitie in the furnishing of themselves with such knowledge by Practicall Instrumentall operation, when their more weighty negotiations will not permit them for Theoreticall figurative demonstration; those that are guilty of the aspertion, and are touched therewith may answer for themselves, and studie to be more Theoreticall, than Practicall: for the Theory, is as the Mother that produceth the daughter, the very sinewes and life of Practise, the excellencie and highest degree of true Mathematicall Knowledge: but for those that would make but a step as it were into that kind of Learning, whose onely desire is expedition, and facilitie, both which by the generall consent of all are best effected with Instrument, rather then with tedious regular demonstrations, it was ill to checke them so grosly, not onely in what they have Practised, but abridging them also of their liberties with what they may Practise, which aspertion may not easily be slighted off by any glosse or Apologie, without an Ingenuous confession, or some mentall reservation: To which vilification, howsoever, in the behalfe of my selfe, and others, I answer; That Instrumentall operation is not only the Compendiating, and facilitating of Art, but even the glory of it, whole demonstration both of the making, and operation is soly in the science, and to an Artist or disputant proper to be knowne, and so to all, who would truly know the cause of the Mathematicall operations in their originall; But, for none to know the use of a Mathematicall Instrumen[t], except he knowes the cause of its operation, is somewhat too strict, which would keepe many from affecting the Art, which of themselves are ready enough every where, to conceive more harshly of the difficultie, and impossibilitie of attayning any skill therein, then it deserves, because they see nothing but obscure propositions, and perplex and intricate demonstrations before their eyes, whose unsavoury tartnes, to an unexperienced palate like bitter pills is sweetned over, and made pleasant with an Instrumentall compendious facilitie, and made to goe downe the more readily, and yet to retaine the same vertue, and working; And me thinkes in this queasy age, all helpes may bee used to procure a stomacke, all bates and invitations to the declining studie of so noble a Science, rather then by rigid Method and generall Lawes to scarre men away. All are not of like disposition, neither all (as was sayd before) propose the same end, some resolve to wade, others to