MR. F. C. PENROSE ON THE ORIENTi^TION OF CERTAIN 
With respect to the temple near Thebes, published in the former list, p. 831, some 
magnetic observations have been sent me which show an orientation cliffering by 
about 90° from that which I had deduced from my observations- The latter are 
perfectly consistent amongst themselves, but as I cannot affirm the impossibility of 
some accidental error, it seems best to withdraw that temple from the list, at least 
for the present. 
The order in which the examples given below are placed, is simply that in which 
they were examined. 
In the elements which follow, the rules which have been observed wdth respect to 
the sun’s depression and the altitude of the stars, when heliacal, are generally in 
accordance with the remarks made above on the visibility under such circumstances 
of the different magnitudes. In some cases the altitudes are affected by the height 
of the visible horizon. The propriety of these rules appears to be strengthened by 
the statement of Biot, as derived from Ptolemy, in his ‘ Ptecherchessurl’Annee Vague 
des P/gyptiens, p. 58, namely, that in Egypt the sun’s depression for heliacal purposes 
was considered to be 11°. And as it has been shown Vjy Sir J. N. Lockyer in ‘ The 
Dawn of Astronomy that such stars as a Cohnnbce and y Draconis were included 
among those used for the Egyptian temples, 11° would be very suitable for a general 
rule: although so deep a depression would be unnecessary for a star of the first 
magnitude, as I have personally noticed in Greece. In a great many cases I have 
added the effect produced upon the dates by the variation of some of the elements. 
But the dates which follow the rule I believe to be the most probable, as well as the 
most systematic. The calculations have all been carried out to seconds of arc and 
time, l)ut the results as entered, are restricted to the nearest minute. The years of 
the dates of the temples can, ol course, be only considered as approximate ; relatively, 
however, they may be more im])licitly trusted. The days of the month given are 
less uncertain, as they depend upon the sun’s place, which results immediately from 
the orientation. It is an important element, as marking the time of year of the 
principal festivals. 
As respects the identification of the stars there is seldom much uncertainty. In 
the first place, for solar temples the possible stars are so few. Thirteen stars and 
two constellations, the Pleiades and Acpiarius, make up the wdiole list of those that 
are l)oth bright enough and near enough to the ecliptic to be seen heliacally in con¬ 
nection with the sun through the narro^v eastern or w'estern openings ; and six of 
the thiiteen stars, including two of the brightest, viz., Aldebaran and Begulus, do 
not appear to have been used. 
In the former paper, p. 819, I described briefly some of the methods which may be 
followed in the search for the star. That which I have myself adopted is here rather 
more fully explained. On a stereographic projection of the sphere, taken on the pole 
of the ecliptic, using a mean obliquity, the pole of the equator is also shown, with 
B.A. hour-lmes and parallels of declination, and upon it also the principal available 
