Archimedes Texts

SAGR. I may then, it seems, for once prove a Master to you both.
And because the proceeding by interrogatories doth in my opinion
much dilucidate things, besides the pleasure which it affords of con
founding our companion, forcing from him that which he thought he
knew not, I will make use of that artifice. And first, I suppose that the
Ship, Gally, or other Vessel, which we would discover, is a great way
off, that is, four, six, ten, or twenty ^{*} miles, for that to kenne those

neer at hand there is no need of these Glasses: & consequently, the
Telescope may at such a distance of four or six miles conveniently
discover the whole Vessel, & a muchgreater bulk. Now I demand
what for species, & how many for number are the motions that are
made upon the round top, depending on the fluctuation of the Ship.

* I deviate here
from the strict Sea
Diallect, which
denominatesall di
stances by Leagues.

SALV. We will suppose that the Ship goeth towards the East.
First, in a calme Sea, it would have no other motion than

this of progression, but adding the undulation of the Waves,
there shall result thence one, which alternately hoysting and low
ering the poop and prow, maketh the round top, to lean forwards
and backwards; other waves driving the vessel sidewayes, bow the
Mast to the Starboard and Larboard; others, may bring the ship
somewhat abovt, and bear her away by the Misne from East, one

while towards the ^{*} Northeast; another while toward the South
east; others bearing her up by the Carine may make her onely to
rise, and fall; and in sum, these motions are for species two, one
that changeth the direction of the Telescope angularly, the other
lineally, without changing angle, that is, alwayes keeping the
tube of the Instrument parallel to its self.

* Greco, which
the Latine Tran
slator according to
his usual carelesse
nesse (to call it no
worse) translates
Corum Ventum,
the Northwest
Wind, for Ventum
Libanotum.

SAGR. Tell me, in the next place, if we, having first directed

the Telescope yonder away towards the Tower of ^{*} Burano, six
miles from hence, do turn it angularly to the right hand, or to the
left, or else upwards or downwards, but a ^{*}straws breadth, what ef

fect shall it have upon us touching the finding out of the said tower?

SALV. It would make us immediately lose sight of it, for such
a declination, though small here, may import there hundreds and

thousands of yards.

SAGR. But if without changing the angle, keeping the tube
alwayes parallel to it self, we should transfer it ten or twelve
yards farther off to the right or left hand, upwards or downwards,
what alteration would it make as to the Tower?

SALV. The change would be absolutely undiscernable; for
that the spaces here and there being contained between parallel
rayes, the mutations made here and there, ought to be equal, and
because the space which the Instrument discovers yonder, is capa
ble of many of those Towers; therefore we shall not lose sight of it.

SAGR. Returning now to the Ship, we may undoubtedly af
firm, that the Telescope moving to the right or left, upwards, or