OF THE GREAT PYRAMID. 699 



because what was mentioned previously admits of easier investigation as to its 

 truth, and is perfectly sufficient for its purpose, — viz., to show that the first and 

 chief sacred Jewish measure of time, as well as their sacred measure of space, 

 "which they had received long before they went down to Egypt," is embodied, 

 though in terms unintelligible and unmeaning to Egypt, in the Great Pyramid. 



Date of Pyramid. 



In the matter, however, of time, on the large scale, attention may be profit- 

 ably drawn to some further points connected with fig. 6, Plate XXVI. 



The angle of the passage entrance, measured by Col. Howard Vyse, at W 41', 

 has been settled by so excellent an authority as Sir John Herschel in the astro- 

 nomical world, as meaning the lower culmination of a Draconis, the pole star of 

 the time ; and which Sir John has computed at 26° 15' 45", for the year 2121 

 B.C. ; whence, if the Colonel's angle be well measured, we may deduce from the 

 annual precession in North Polar Distance for that part of the sky, viz., + 18" per 

 annum, that the date of the Pyramid passage in question is earlier by about 

 eighty-three years, or is to be fixed at 2204 b.c. 



Yet, if there be force in our general conclusions, as to the less value for 

 scientific ends in the descending, than the ascending portion of the interior, — it 

 will be more proper to take either the theoretical angle, which gives the inter- 

 sections at D, (Plate XXVI.) ; or, the practical angle of the Grand Gallery, 

 measured by the French at 25° 55' and 26° 0', but by Col. Howard Vyse at 26° 18', 

 and computed by myself at 26^ 18' IC; and then we have for the date, 2129 b.c* 



* In further elucidation of the note on page 686, and the number 5"672, chosen as the best 

 resulting value from Bailt's Experiments for the Mean Density of the Earth, it may be mentioned, 

 that in the last page of his valuable memoir, he gives the following several numbers as the exact 

 foundations for his more popular announcement of 5-675, and desirjes his future readers to form 

 their own idea of the real mean amongst them ; viz. : — 



Mean of all the observations without exception, .... 5-6747 



The same, when one series of doubtful observations has been abstracted, . 5-6754 



The same, with a second doubtful series also abstracted, . . . 56666 



The same, with a third doubtful series also abstracted, . . . 5-6683 



The same, with a fourth doubtful series also abstracted, . . . 5-6604 



Now, the simple mean of all these comes out 5-66908, but as that evidently gives too much 

 importance to the latter results, which Mr Baily did not allow to appear at all in the 5-675, — let 

 \ us take a mean of the two, and we have 5-67204. 



Again, if it be agreed that the first result is five times the weight of any one of the others, and 

 then take the mean accordingly, we have 5-67158. Or, if it be further settled, that the same rea- 

 sons which make the first more weighty than the second, make the second somewhat more weighty 

 than the third, and so on to the fifth ; that is, that every subsequent given result represents a less 

 .number of observations, — let us multiply the first by 10, and the others by 4, 3, 2, and 1, when we 

 have for this form of the mean, 5-67227. And putting all these three probable means together, 

 5-67204, 5-67158, and 6-67227, — there appears for the final mean, 5-67196 : sufficiently repre- 

 sented by our 5-672. 



VOL. XXIII. PAKT III. 9 B 



