194 



KNOWLEDGE 



[Jan. 6, 1882. 



sently rcaili tho northern face of the Pyramid. By again 

 using a well-known property of liquids, however, combined 

 with a well-known property of light rays, they would con- 

 tinue the process of orienting to a much greater height. 

 (When I say well-known, T mean well-known to them : 

 they were manifestly skilful engineers and architects, and 

 iis surely .■vs they were wi'll acquainted witii the properties 

 of matti^r, so surely must they have been actiuainted with 

 the mathematical relations on which the simpler optical 

 laws depend. Possibly they knew laws more recondite ; 

 but the simpler laws they certainly know.) Now, the plan 

 which would (juickly suggest itself to anyone knowing these 

 laws, woukl be to make use of the reflected rays fi-om a star 

 when the direct rays could no longer be employed. We 

 know that when a ray from a luminous ol>ject is reflected 

 at a plane surface, the reflected ray and the incident ray 

 make equal angles with a lino perpendicular to the surface 

 at the point of incidence, and are also both in the same plane 

 with that perpendicular. Now, what the Pyramid archi- 



which are taken from Smyth's book, " Our Inheritance in 

 the Great Pyramid," shows. AE is the long, slant passage, 

 which for convenience we may call the descending passage, 

 I3C is an ascending passage of exactly the same character, 

 which, therefore, we might have presumed was intended for 

 a similar purj)ose, e\en if the consideration of the natural 

 course which intelligent l)uildors would liave pursued had 

 not led us to e.xpect to And precisely such an ascending 

 passage here. But it may be asked how the reflected rays 

 from the star were obtained 1 Nothing could have been 

 simpler. The very same process which had been applied 

 in levelling would be all that would be needed here. If 

 the descending passage were for a time (a day, or even an 

 hour would suftice) plugged at B, and water poured in 

 so as to partially fill the angle thus formed at B, the 

 surface of that water would reflect the rays of Alpha 

 Draconis up the ascending passage BO. The direction for 

 the south line thus indicated could be marked, and then 

 the plug left to slide down to the subterranean chamber. 



tocts wanted was to have a constant means of determining 

 the direction of north and south — in other words, a con- 

 stant knowledge of the position of what modern astronomers 

 call tlio plane of the meridian. They had this so long as 

 they could observe the Polivstar wlien due north, through 

 a passage opening out within the square layer they were 

 adding to the Pyramid. Wln^n, as their work continued, this 

 passage opened out in the partof the sloping side already com- 

 pleted, tliey could .still dotrmine the meridian plane if they 

 carried up a passage through the masonry in such a direc- 

 tion as to contain the rays from the Pole-star after reflec- 

 tion at a horizontal surface, such as that of still water. 

 For a poipendicular to the surface of still water is directed 

 to the zenith, and tlio direct and reflected rays ft-om the 

 star (due north) lie, therefon^, in the meridian plane which 

 passes through the north and south points and through the 

 zenith. 



Now this is precisely what the Pyramid builders seem to 

 have done, as tlie accompanying tigure, the dimensions of 



Once a year (supposing one layer of stones added each 

 year, as Lepsius surmises) would have sutticed for this 

 operation. 



Not only do we thus find a natural and perfect explana- 

 tion of the circumstance (hitherto unexplained) that the 

 ascending passage is inclined at the same angle to the 

 horizon as the descending passage, but precisely as we 

 might e.xpect from a true theory, wo find that other points 

 of difiiculty have here their explanation. It is olivious that 

 at B the casing stones of the descending passage would have 

 to be very closely set and carefully cemented, so that the 

 water used, year after year, in obtaining the reflected rays, 

 might not percolate through and do mischief. Now, just 

 here, we find the stones of the descending passage arranged 

 with greater precision and made of better material. 

 " Whj'," says Smyth — who notices everything, but seems 

 always to insist on some forced explanation — " why did 

 the builders change the rectangular joint at that point, and 

 execute such unusual angle as they chose in place of it, 



