108

APPENDIX.

passage may be said to have been directly pointed at a Draconis
at its inferior culmination, at which moment its altitude above the
horizon of Gizeh (lat. 30) would have been 27° 9'—refraction
being neglected as too trifling (about 2) to affect the question.
The present polar star a Ursse Minoris was, at that epoch, 23°
more or less in arc from the then pole of the heavens, and, of
course, at its lower culmination, it was only 7° above the horizon
of Gizeh.

No other astronomical relation can be drawn from the
table containing the angles and dimensions of the passages, for
although they all point within five degrees of the pole of the
heavens, they differ too much and too irregularly to admit of any
conclusions.

The exterior angles of the buildings are remarkably uniform,
but the angle 52° is not connected with any astronomical fact, and
was probably adopted for architectural reasons.

CALCULATIONS.

Por. of a. Draconis for 1039.

R.A., 1830 =13" 59'" 46'6 Due 1830 =65° 11' 20" (See Ast. Soc. Cat.)

Precession + 9 years= + 14'-G Pre. + 9 years = — 2 30

14 0 1 -2 05 8 50 =S for 1839.

Reduced to Arc 210° 0' 18"=*

Precession in Longitnde for + 1 year, epoch 1800 ......... + 50"-22350

Variation for 2000 years backwards, to obtain a mean 1 ~ 0-1886

rate of precession for 4000 ......... J + 5Q- 17464

Ulultiply by years ......... — 4000

Precession in Long. = — 200G97"'5G = — 55° 44' 57" 56 ... — 200697-56000
or correctly enough for the purpose ... ... 55° 44' 58"

P the present place of the north pole.

P' its place 4000 years ago.

a the star • Draconis.

£ its projection on the equinoctial.

TP — £ = 210° 0' 18" - x
T === = 180

=== H— 30 0 18 = angle *>• V a

In Spherical Triangle P 11 P'.
Given angle P n P = 55° 44' 58".
Pn = P'n = obliquity of ecliptic at a
mean epoch, 2000 yeare back.