204 The Great Pyramid in Egypt, [April, 



on that never-ending subject, the probable error of even the 

 best modern determination ; and also on that long felt 

 physical doubt, as to the want of perfect constancy in 

 relative position through long ages, between the crust of 

 the earth and the direction of its axis of rotation. 



But there is more important astronomy in the Great 

 Pyramid than merely for geographical position. 



The one only entrance passage, as already stated, looks 

 out northward in the plane of the astronomical meridian 

 and at the height almost of the polar point itself. Now 

 certain well-meaning naval officers, about fifty years ago 

 announced that, having descended that passage a certain 

 distance at night, they saw, on looking up towards its 

 mouth, the polar star, viz., a Ursae Minoris, most 

 clearly ; whence they inferred, that the passage must have 

 been built for the purpose of observing that same star in 

 ancient times. 



On this statement being submitted in 1839 Dv Col. 

 Howard Vyse, when he had returned from North Africa, to 

 Sir John Herschel, then just returned likewise from his cele- 

 brated astronomical sojourn in South Africa, he at once 

 said,* These gentlemen have failed to take into account the 

 Precession of the Equinoxes, which, in 4000 years, would 

 have displaced every star in the heavens, from its then 

 apparent position on the sphere by no less a quantity than 

 55 45' of longitude, and would have changed all the 

 relations of the constellations to the diurnal sphere ; whence 

 it comes that the present pole star could by no possibility 

 have been seen at any time in the twenty-four hours through 

 the entrance passage into the Great Pyramid. But there was 

 another star, he added, then almost exactly in that line, viz., 

 a Draconis, and that must therefore have been the polar star 

 of reference for the pyramid builders; the passage being built 

 at such a vertical angle, in the meridian, as to point to that 

 star at its transit beneath the pole, and at that precise date 

 when Precession had made the star's distance therefrom to 

 amount, for the time, to 3 42', or whatever the observed 

 deficit of the passage angle below 30 might be. 



This suggestion of Sir John Herschel's certainly intro- 

 duced another, and in so far a dangerous, mode of explaining 

 one passage angle which we have already got approximately 

 from a very different consideration. In this latter case, 

 however, the quantity was merely an auxiliary, while in Sir 

 John Herschel's explanation we have the ultimate natural 



* See p. 107, vol. ii., of Vyse's " Pyramids of Gizeh." 



