July 2, 1891] 



NATURE 



199 



ON SOME POINTS IN THE EARLY HISTORY 

 OF ASTRONOMY.-^ 



IT is imperative to be perfectly definite and clear on the 

 question of the amplitudes above 26° at Thebes. Any 

 amplitude within 26' means that up to that point the sun 

 at sunrise or sunset could be observed some day or days of 

 the year — once only in the year if the amplitude is exactly 

 at the maximum, twice if the maximum is not reached. 

 But in the case of these temples with greater amplitudes 

 than 26^, it is quite clear that they can have had nothing 

 to do with the sun. Is there, then, any additional line of 

 evidence that the Egyptians used these temples to observe 

 the stars ? Here a very interesting question comes in ; 

 a temple built at one period to observe a star could not 

 go on for ever serving its purpose, for the reason that 

 the declination of the star must change by precession. 

 Therefore a temple built with a particular amplitude to 

 observe a particular star, useful for one period would be 

 useless for another. 



We have here possibly a means of testing whether or 

 not any of these temples were used to observe the stars. 

 In those very early days, 3000 or 4000 years B.C., we must 

 assume that the people who observed the stars had not the 

 slightest idea of these possible precessional changes ; they 

 imagined, that they were just as safe in directing a temple 

 to a star as they were in directing a temple to the sun 

 But with a star changing its declination in an average 

 way, the satne temple could not be used to observe the 

 same star for more than 200 or 300 years ; so that at the 

 end of that time, if they still wished to observe that par- 

 ticular star, they must either change the axis of the old 

 temple, or build a new one. 



As a matter of fact, we find that the axes of the temples 

 have been changed and have been freely changed ; that 

 there has been a great deal of work done on many of 

 these temples which are not oriented to the sun, in order 

 to give them a twist. 



Once a solar temple a solar temple for thousands of 

 years ; once a star temple only that star temple for some- 

 thing like 300 years, so that the conditions were entirely 

 changed. 



We get cases in which the axis of a temple has had its 

 direction changed, and others in which, where it has been 

 difficult or impossible to make the change in a temple, 

 the change of amplitude has been met by putting up a 

 new temple altogether. We are justified in considering 

 such temples as a series in which instead of changing 

 the orientation of a pre-existing temple, a new temple has 

 been built to meet the new condition of things. That, I 

 think, is a suggestion which we are justified in making to 

 Egyptologists on astronomical grounds. 



We cannot, of course, make it with absolute certainty, 

 for the reason that in the case of most of these temples 

 the best Egyptologists cannot give us the most precious 

 piece of information which we require from the astronomi- 

 cal point of view. That is the date of XhQ foundation of 

 the temple. If in the case of these temples it were abso- 

 lutely certain that each temple was built at a certain time 

 with a certain orientation, the use of the precessional 

 globe would tell us at once whether or not that temple 

 was pointed to any particular star. Some other astro- 

 nomical considerations may here come to our help. If 

 the north polar distance of a star is increasing — that is, 

 if it is increasing its distance from the north pole — its de- 

 clination is being reduced, and the orientation of the 

 temple would be gradually becoming more and more 

 parallel to the equator ; if the declination of the star be 

 increasing, then the orientation of the temple would have 

 had to be more and more north or south. The change 

 in the orientation, therefore, could give us important 



information, and ultimately we might be able to determine 

 what the name of that particular star was. At present the 

 matter must remain more or less as a suggestion ; but 

 if anything like approximate dates can be given, then 

 astronomy really may come to the rescue of the Egypto- 

 logist and archaeologist generally, and repay that debt to 

 which I have referred, which she owes to so many other 

 sciences. 



Although, however, these matters can be discussed 

 in a way that will indicate that the inquiry is raised, 

 I do not wish for one moment to speak of it as 

 being settled, because the observations which have been 

 made already in Egypt with regard to the orientation of 

 these temples have not been made from such a very 

 special point of view ; and further some alteration in the 

 amplitude would be made by the presence of even a low 

 range of hills miles away from Thebes in the case of a 

 star rising or setting pretty nearly north or south. No 



Fig. 14.— The two temples at Medinet Abou, showing the change in their 



orientation. 



NO. II3I, 



' Continued from p. 



VOL. 44] 



one would care to make the assertion with absolute 

 definiteness until it was known whether or not the horizon 

 in each case was interfered with by hills or any inter- 

 vening objects — was or was not one, in fact, which might 

 be regarded as a sea horizon from the point of observa- 

 tion ; if there were impediments, the angular height of 

 them must, of course, be exactly known. 



To continue this observation and this kind of thought 

 a little further, we will go back to Karnak generally. In 

 the first place we have the magnificent solar temple. 



Next we have two parallel temples, one of them a late 

 addition to the solar temple itself, and another one 

 parallel to it, each of them with an amplitude of 63^, 

 one N. of E., the other S. of W. We have then two 

 parallel temples at right angles to the solar temple at 

 Karnak. We have also a temple, with an azimuth of 

 68' N. of E., and one, probably older still, with an ampli' 



