Thomas Digges, in his treatise on the Newe Science of Great Artillerie,
came much nearer the truth; for he remarked[141], that "The bullet
violentlye throwne out of the peece by the furie of the poulder hath two
motions: the one violent, which endeuoreth to carry the bullet right out
in his line diagonall, according to the direction of the peece's axis,
from whence the violent motion proceedeth; the other naturall in the
bullet itselfe, which endeuoreth still to carrye the same directlye
downeward by a right line perpendiculare to the horizon, and which dooth
though insensiblye euen from the beginning by little and little drawe it
from that direct and diagonall course." And a little farther he observes
that "These middle curve arkes of the bullet's circuite, compounded of
the violent and naturall motions of the bullet, albeit they be indeed
mere helicall, yet have they a very great resemblance of the Arkes
Conical. And in randons above 45° they doe much resemble the Hyperbole,
and in all vnder the Ellepsis. But exactlye they neuer accorde, being
indeed Spirall mixte and Helicall."
Perhaps Digges deserves no greater credit from this latter passage than
the praise of a sharp and accurate eye, for he does not appear to have
founded this determination of the form of the curve on any theory of the
direct fall of bodies; but Galileo's arrival at the same result was
preceded, as we have seen, by a careful examination of the simplest
phenomena into which this compound motion may be resolved. But it is
time to proceed to the analysis of his "Dialogues on Motion," these
preliminary remarks on their subject matter having been merely intended
to show how long before their publication Galileo was in possession of
the principal theories contained in them.
Public-domain text, read in full here on John Shaqi.
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