"رحلات السيد بيترو ديلا فالي، وهو نبيل روماني، إلى الهند الشرقية وصحراء الجزيرة العربية. وفيها يصف بدقة البلدان المختلفة، وكذلك العادات، الأعراف، التجارة، الطقوس الدينية والمدنية، لهؤلاء الأمراء وتلك الأمم الشرقية: في رسائل وديّة إلى صديقه السيد ماريو سكيبانو. وتم إضافة سرد عن رحلة السير توماس رو إلى جزر الهند الشرقية" [‎٧] (٥٠٨/٢٨)

Into the EAST-INDIES.
7
but fomething rough. Every day about the hour of noon the
Sun's altitude was infallibly obfervd , not onely by the Pilots;,
as the cuftom is in all {hips, and the Captain, (who was a good
Seamanj and perform'd all the exercifes of Art very well) but
( which pleas'd me moft 3 and which I thought worthy of great
praife and imitation J there was no day, but at that hour twenty
or thirty mariners;, mafters, boys, young men, and of all forts
came upon the deck to make the fame obfervation > fomewith
Aftrolabes, others with Crofs-ftaffs, and others with feveral
other inftruments, particularly with one which they told me
was lately invented by one and from his name call d ^17cf*?
David' s-Jiaff. This Inftrument confifts of two Triangles united
together, one longer then the other, both having their bafe
arch'd, and between them in the circle of their bafes containing
' an intire quadrant of ninty degrees. But whereas the fhorteft
Triangle, whole Angles are lefs acute ^ contains fixty degrees
divided by tens ( according to cuftom) in the circle of its bafe,
which are two thirds of a quadrant, the other longer and of
acuter Angles, which extends much backward, and opens in a
wider circle at the bafe,comprehends no more then thirty, which
make the remainder of the quadrant 5 fo that the longer Triangle
contains fewer degrees by half then the fhorter j and he that
would have the degrees larger for the better Subdividing them
into minutes, may make the circle or bafe of the leffer Triangle
take up feventy degrees, and fo there will remain to the longer
no more then twenty for the complement of the quadrant. Ac
cording to this diftribution, the degrees in the longer Triangle
will come to be fo large, as to be capable of the fmalleft divifion
of minutes ^ a thing very important. Befides, it hath two Fanes
or Sights, in each Triangle one, which are to be mov'd back
ward and forward ^ and with thefe, that is, with that of the
long Triangle, the level of the Horizon is taken 5 and with the
other of the fhort Triangle, that of the Sun 5 with this fur
ther conveniency, that the Sights being lufficiently large, are
therefore very expedient for performing the operation with
fpeedj notwithftanding the dancing of the fhip when the Sea is
rough 5 in which cale^if the Sights be toofmall 5 Vis hard to make
any obfervation. With this Inftrument, and feveral others,
many of the Englifti perform'd their operations every day 5 fuch
as knew not how to do them well, were inftruded^ and if any
one err'd in computation or otherwife,his error was (hew d him,
and the reafon told him, that fb he might be train d to work
exactly : The opinion of the fkilful was heard, and taken notice
of 3 and at length all the obfervations being compar d together,
the Pilot and the Captain refolv'd, and with mature counfel de~
termin'd ofall by which means their voyages are very well
manag'd, and almoft always fucceed profperoufly to them. In
the Portugal fhips I hear the contrary comes to pafs 5 becaule
the Pilots being extremely jealous of their affairs (an habitual