t numbre of them were wroughte, that they may be practised
in this tyme also. Wherby shallbe plainly perceaued, that many
thynges seme impossible to be done, whiche by arte may very well
be wrought. And whan they be wrought, and the reason therof not
vnderstande, than say the vulgare people, that those thynges are
done by negromancy. And hereof came it that fryer Bakon was
accompted so greate a negromancier, whiche neuer vsed that arte
(by any coniecture that I can fynde) but was in geometrie and
other mathematicall sciences so experte, that he coulde dooe by
theim suche thynges as were wonderfull in the syght of most
people.

Great talke there is of a glasse that he made in Oxforde, in
whiche men myght see thynges that were doon in other places, and
that was iudged to be done by power of euyll spirites. But I
knowe the reason of it to bee good and naturall, and to be
wrought by geometrie (sythe perspectiue is a parte of it) and to
stande as well with reason as to see your face in common glasse.
But this conclusion and other dyuers of lyke sorte, are more
mete for princes, for sundry causes, than for other men, and
ought not to bee taught commonly. Yet to repete it, I thought
good for this cause, that the worthynes of geometry myght the
better be knowen, & partly vnderstanding geuen, what wonderfull
thynges may be wrought by it, and so consequently how pleasant
it is, and how necessary also.

And thus for this tyme I make an end. The reason of som thynges
done in this boke, or omitted in the same, you shall fynde in
the preface before the Theoremes.

The definitions of the principles of
_GEOMETRY_.

Geometry teacheth the drawyng, Measuring and proporcion of
figures. but in as muche as no figure can bee drawen, but it
muste haue certayne boundes and inclosures of lines: and euery
lyne also is begon and ended at some certaine prycke, fyrst it
shal be meete to know these smaller partes of euery figure, that
therby the whole figures may the better bee iudged, and
distincte in sonder.

[Sidenote: A poincte.] _A Poynt or a Prycke_, is named of
Geometricians that small and vnsensible shape, whiche hath in it
no partes, that is to say: nother length, breadth nor depth. But
as their exactnes of definition is more meeter for onlye
Theorike speculacion, then for practise and outwarde worke
(consideringe that myne intent is to applye all these whole
principles to woorke) I thynke meeter for this purpose, to ca