76 Mr. F. C. Penrose. On the Orientation of Greek 



same as that described by Mott as a distinct part of the antero- 

 lateral tract of Gowers, and is certainly no artifact, as has been sug- 

 gested by Patrick. 



" On the Orientation of Greek Temples and the Dates of their 

 Foundation derived from Astronomical Considerations, 

 being a Supplement to a Paper published in the 4 Trans- 

 actions of the Royal Society,' in 1893." By F. C. Penrose, 

 F.R.S. Received February 24,— Read March 11, 1897. 



(Abstract.) 



The paper first states briefly the link which connects this branch 

 of archaeology with astronomy, namely thus : — The great temple 

 functions were celebrated at early dawn, the principal annual func- 

 tion being on the day when the sun, rising above the visible horizon, 

 shone along the axis of the temple, through the eastern door, upon 

 the Statue of the Deity in the sanctuary, the axis of the temple 

 having been so directed at its foundation — an institution which 

 seems to have originated in Egypt, but which was, from the earliest 

 times, adopted in Greece. But as some time was required by the 

 priests for preparation for the ceremony, in the absence of clocks, 

 the rising or setting of an heliacal star would have to be observed 

 from the sanctuary to give warning of the sun's approach ; and it 

 would be the case, roughly, that when such star could be just seen 

 either at its appearing in the east, or just before its disappearance 

 in the west, it would give about an hour's time for preparation. 

 The data for the calculation are : the latitude, the amplitude given 

 by the direction of the temple's axis and the altitude of the visible 

 horizon. From these the sun's right ascension and declination are 

 deduced, then the place of a star having been found suitable for 

 acting as a warning star — which could not have been always possible 

 without original contrivance — the precessional movement of such star 

 will then give the period which has elapsed since it was in accurate 

 heliacal correspondence with the sun. 



In the paper are recorded some observations of the heliacal visi- 

 bility of stars chiefly before sunrise, and the different angles of solar 

 depression which seem to me to be required for stars of different 

 magnitudes, and particularly as to the visibility of the Pleiades in 

 twilight. 



Then the elements of orientation of a number of temples are 

 given, viz., four from Athens, which were not included in the former 

 series, a new determination of the ancient Heraeum near Argos, the 

 former having been taken before the site was completely cleared ; 

 of the temple of Apollo at Delphi, of which the site is very 



