146 Attempt to ascertain Date of Stonehenye from its Orientation. 



of the leaning stone, and the want of verticality, parallelism, and 

 straightness of the inner surfaces of the opening in the N.E. trilithon, 

 we are justified in adopting the azimuth of the avenue as that of the 

 temple. 



Next, with regard to the determination of the azimuth of the 

 avenue as indicated by the line of pegs to which reference is made in 

 the body of the paper. The small angle between the nearest pegs 

 A and B (which are supposed to be parallel to the axis of the avenue), 

 observed from station a, was measured, and the corresponding calcu- 

 lated correction was applied to the ascertained true bearing of the 

 more distant peg B. 



Thus 



True bearing of peg B = 238 35' 0" 



Calculated correction to peg A = 12 8 



True bearing of line AB 238 47 8 



Bearing of Salisbury Spire 189 8 20 



True bearing of a line parallel to the 

 axis of near part of avenue N. 49 38 48 E. 



The moan of the three independent determinations by another 

 observer was 49 39' 6". 



The calculated bearing of the more distant part of the axis of the 

 avenue determined in the same manner by observations from station I 

 is 49 32' 54". The mean of the two, namely, 49 35' 51", justifies 

 the adoption of the value 49 34' 18" as given by the Ordnance Survey 

 for the straight line from Stonehenge to Sidbury Hill. 



(3.) Observation of Sunrise. -On the morning of June 25, 1901, sun- 

 rise was observed from station a, and a setting made as nearly as 

 possible on the middle of the visible segment as soon as could be 

 done after the Sun appeared. 



The telescope was then set on the highest point of the Friar's Heel, 

 nnd the latter was found to lie 8' 40" south of the Sun. 



Sun's declination at time of observation... 23 25' 5" 

 Elevation of horizon at point of sunrise ... 35 48 

 Assuming 2' vertical of Sun to have been 

 visible at observation, we have ap- 

 parent altitude of Sun's upper limb 37 48 



Refraction -27' 27" "1 _^ ^ -.Q 



Parallax ..+ 9 J 



True altitude of upper limb 10 30 



Sun's semi-diameter . 15 46 



True altitude of Sun's centre . -0 5 16 



