March 10, 1882.] 



• KNOWLEDGE 



399 



SeeiiiLj tliis, and observing that the ascending and de- 

 scending passages are just such as the astronomer would 

 make to secure such a result, we may accept, without a 

 particle of doubt, the belief that they were made for that 

 pwrfos-*. 



Then we saw that the features of the Great Ascending 

 Gallery were not such as would he essential, or even de- 

 sirable, to increase or maintain the accuracy of the orienta- 

 tion, as layer after layer was added to the Pyramid, but 

 are precisely such as would be essential if tlie Pyramid was 

 meant to subserve (as one, at least, of its objects) the 

 puq>ose of an observatory. 



But persons unfamiliar with astronomy will say (several 

 have said so in letters addressed to me). This great ascending 

 gallery would only enable astronomers to observe stars 

 when due south, or nearly so, and only those which, when 

 due south, were witliin a certain distance above or below 

 the point towards wliicli the axis of the Great Galler}' is 



imagines that to be the chief observing instrument The 

 comparatively unobtrusive transit circle seems far less im- 

 portant. But the time observations, which are far and away 

 the most important oltservatious made at Greenwich, are all 

 made, or at least, all regulated, by the transit observations. 

 So are tlie observations for determining the positions of 

 stars. 



When the equatorial is used to make a time or posi- 

 tion observation, it is used as a diflerential instrument, it 

 is employed to determine how far east or west a star may 

 be (theoretically, how much it differs in right ascension 

 nieasured by time) from another ; and again, to show how 

 far north or south a star may be (theoretically how much 

 it differs in declination) from another, whose right ascen- 

 sion and declination have already been determined by re- 

 peated oViservations with the transit circle. Similarly, the 

 altitude and azimuth instrument is used in direct subor- 

 dination to the transit circle. 



Vertical Section of the Pyramid Observatory throagh the plane of the passages and gallery, showing the range cf view of the 



great observing tnbe. 



directed. Were all the other stars left unobserved 1 Asid 

 again, we know that the Egyptians, like all ancient astro- 

 nomers, paid great attention to the rising and setting of 

 the heavenly bodies, and especially to what was called the 

 heliacal rising and setting of the stars. In what way 

 would the Great Gallery help them here 1 



Now, with regard to the first point, we note that the 

 chief instrument of exact observation in modern observa- 

 tories, the one which, as it were, governs all the othere, has 

 1 precisely this quality — it iaahrai/s directed to the meridian, 

 and has, indeed, a very much narrower range of view on 

 ! either side of the meridian than the Great Gallery had. 

 I And though it is indeed free to range over the whole arc of 

 I the meridian from the south horizon point through the point 

 i overhead to the north horizon point, it is mainly employed 

 1 over about that range north and south of the celestial 

 : equator which was commanded by the Great Gallery. 

 The visitor at Greenwich sees the great equatorial, and 



The astronomers who observed from the Great Pyramid 

 doubtless made many more observations off the meridian 

 than on it. They made multitudinous observations of the 

 rising and setting of stars, and especially of their heliacal 

 risings and settings (which last, however, though we hear 

 so much of them, belonged ex necessitate to but a ^ery 

 rough class of observations). They no doubt often used 

 astrolaV)es and similar instruments to determine the posi- 

 tions of stars, planets, comets, &c., when off the meridian, 

 with reference to stars whose places were already deter- 

 mined by the use of their great meridional instrument. 

 But all those observations were regulated by, and derived 

 their value from, the work done in the Great Ascending 

 Gallery. The modern astronomer sees that this was the 

 only way in which exact observations of the heavenly 

 bodies all over the star-sphere could possibly have been 

 made ; and seeing the extreme care, the most marvellous 

 pains, which the astronomers of the Great Pyramid took to 



