I 



CORRESPONDENCE 267 



the distance between P and C remaining constant, while PE varies between 



23° 25' 47' and 35° 25' 47". 



The conditions which may be presumed to have prevailed during the ' winter ' 

 have been ably described by Major R. A. Marriott in his article " The Ice 

 Age Question Solved " (Science Progress for April 1919), while those 

 of the ' summer ' must be very like those of the present era. It occurred to 

 the present writer that it would be interesting to examine the ' spring ' 

 conditions, and he therefore calculated the obliquity at that epoch when PC 

 and EC are at right angles to each other. (This is a simple problem ; PC 

 and CE being given, in a right-angled spherical triangle, to find PE ; cos 

 PC X cos CE = cos PE.) 



What was his amazement on finding it worked out to 29° 58' 53''o 1 I 



The reason for this amazement may not be obvious to the reader, unless 

 he happens to remember that the Great Pyramid of Egypt, the most stupen- 

 dous astronomical monument of antiquity, is situated in North Latitude 



29° 58' 51' (Piazzi Smyth). 

 From which it follows that, at this epoch (5644 B.C.), the Midsummer Sun 

 must have culminated exactly over the centre of the Great Pyramid. The 

 exactness of this accordance will be appreciated when it is remembered 

 that the whole discrepancy, viz. two seconds of arc, when reduced to linear 

 measure, is only 202 feet, whereas the side of the Pyramid itself is about 

 750 feet, or nearly four times as great. 



It is difficult to attribute this coincidence to chance. It looks uncom- 

 monly like design ; for if the ancient architect of the Pyramid wished to 

 erect a gnomon by which to determine the chronometry of the Great Year, 

 he surely would relate it to one of the cardinal points of the cycle. ' spring,' 

 'summer,' 'autumn,' or 'winter'; and of these points in the common 

 year, spring is usually that upon which the thoughts of mankind — of poets 

 and idealists at any rate — are focussed. This assumption of course pre- 

 supposes on the part of the architect a knowledge of the length and other 

 details of the cycle. Yet it also affords criteria by which the feasibility of such 

 an assumption may be tested ; for surely, in that case, the gnomon should be 

 so constructed as to indicate not spring only, but other crucial points in the 

 grand cycle or Great Year. And the question may be asked. Can it do this ? 



Let us see. In the common year, March 21st is referred to as the ' com- 

 mencement ' of Spring ; but June 21st is referred to as mid-summer, not 

 as the ' commencement ' of summer : from which it would seem that 

 March 21st would more fitly be termed mid-spring, and that February 4th 

 when the Sun is half-way between winter and spring should be regarded as 

 the " commencing " of spring. Certainly in the Great Year whose pheno- 

 mena we are considering, the ' commencement,' in this sense, of ' spring ' — 

 that is to say, the point in the cycle at which the angle PCE is 135° — must 

 have been an era anticipated by prehistoric (not preintellectual) mankind 

 only less eagerly than spring itself. And the question arises. Could the 

 Pyramid say when this point had been reached ? 



When the angle PCE is 135° the distance PE, or in other words the 

 Obliquity of the Ecliptic or the Sun's extreme declination in winter, would be 



33° 24' I's 

 and calculating its altitude on December 21st we have : — 

 Altitude of the pole in lat, 29° 58' 51* 



Polar distance of sun ..... 



Gives for angular distance from N. point of horizon 



take from 



Gives altitude of Sun at midday Dec. 21st 



