1883. 115 Trans. N. V. Ac. Set. 



merits of the fourth dynasty, followed by a minute account of the Great 

 Pyramid, and its peculiarities, and a notice of some of the fanciful 

 theories with regard to it, the lecturer proceeded to show that the 

 hitherto neglected difference of angle, between the descending and 

 ascending entrance passage of the Great Pyramid, was really the key 

 to the explanation of the otherwise unexplained fact, that all the pyra- 

 mids have the entrance passage on the northern side, and approxi- 

 mately pointing toward the pole of the heavens. That these passages 

 were intended, or rather that of the Great Pyramid, for some reason, 

 to uoint as near as might be to the then polar star (Alpha Draconis) had 

 already been generally adreiitted, but, in attempting to make this a basis for 

 chronology, there is an uncertainty of some 1300 years in the case of the 

 Great Pyramid, which has the entrance passage pointing about 3° 42' 

 from the true pole. Twice in the processional movement of thestars. Alpha 

 Draconis has been at this distance, once 3400 years B. C. and again 2160 

 years B. C. The former era is adopted by Mr. Proctor in his recent book ; 

 the latter, or near this, by Prof. Piazzi Smyth. Neither of these authors 

 seems to have considered thatthedifferenceof angle between descending 

 and ascending passages was of any particular significance. Mr Proc- 

 tor supposes that observations were made down the ascending passage, 

 by reflection, for purpases of orientation. Some five years ago, the 

 lecturer had suggested this use, not for purposes of orientation, but as 

 indicating, by the change of angle of elevation of the pole star, the in- 

 terval elapsed between the date of the commencement of the pyramid, 

 and the time of arriving at the altitude of the king's chamber, and this 

 difference, 9 minutes of arc, corresponded to twency-five years. More- 

 over, the angle of the ascending passage being the sinaller, indicated 

 that Alpha Draconis had already made its nearest approach to the 

 pole, and was now receding, thus deciding for the later of the two per- 

 iods, z. <?., 2160, or thereabouts, for the date of erection of this pyramid. 



The lecturer proceeded to apply this hypothesis to the other pyra- 

 mids. The so-called third pyramid on the Jeezeh hill, that of Myce- 

 renus, is acknowledged by all to be later than the Great Pyramid, and 

 the angle of the descending passage of this pyramid, as given by Vyse 

 and Perring, when compared with the angle of that of the Great Pyra- 

 mid, as measured by Prof. Smyth, indicates that it was built some 80 

 years later. 



The angles of the entrance passages of most of the pyramids have 

 been very loosely measured, but taking them as they are, and applying 

 the same hypothesis, the lecturer obtained the following results : 



1. Great Northern of Dashoor, about 2410 B. C. 



2. Northern of Abouseer, about 2260 B. C, 



3. The " Second " of the Jeezeh group 2170 B. C. 



