Harriot, Thomas, Mss. 6788

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975488r
Hight of the
ey above the
water in
Surplus of
the Horizon
in
those thinges being regarded which I have specifyed concerning
the staffe: you may henceforward make as true observations as need to
be: the starre or sonne being of any Which before Heretofore seamaster
ship seamaster durst not to trust to the altitude of the sonne or starre
being 60 degrees & upward. because of the difference from the Astrolabe,
imputing the error to the uncertenty in beholding; when as in deed they
know not the abatement I before spake of. the parallaxis & surplus
& that is the cause also of there experimental opening of the Horizon.
And although the error about 30 in stars of ordinary [???] bebe but [???] as al no great
matter of some 10" or there aboute, yet in the hight of 60 & upward it
amounteth to nere a degree, & more. In starres of the largest size
the error was the lesse; but now by reason of the former correction, the
longer & shorter sorte will
ffor taking the sonnes high also by the staffe I thinke good also to
prescribe uncertenty, & to remember unto you the meanes for it
may be done without offense to the
Those men that set a glasse at the end of there staffe or end of the crosse
do [???] subiect them selves to error. It is manifest without any further reason by a common
experiment of looking thorugh glasse windows, that the thinges seene
thourough, are seen distorted, or out of there true places, by reason of refraction
of the visuall beames in the [???] arte of optickes demonstratively appro-
ved. Therefore such meanes I wish to be
The best way that I can præscribe, which some do also use, is to take the high of
the upper edge of the sonne, hiding the whole body with the breadth of the crosse:
And when you have don, to abate 16 minuts; because the diameter or breadth
of the sonne sonne is 32". and then you have the hight of the center of the
sonne which you ought to

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