February i8, 1892J 



NA TURE 



ni 



temple of Der el-Bahari, founded or embellished by Queen 

 Hatshepset (<:/>£•. 1600 B.C.). This temple, instead of being 

 oriented 73° N. of E., lies 26' S. of E., it can never, there- 

 fore, have faced the star observed at Denderah. 



Now, are there any possible explanations .'' Two have 

 suggested themselves to me. 



At Denderah the image of the goddess was taken on a 

 certain day in the year on to the terrace, so that the light 

 of the sun— her father Ra— might fall upon her. 



Building a temple so that the sunlight might enter it 

 once or twice a year (which could not happen in the 

 Denderah temple in consequence of its northern outlook) 

 would enable the aforesaid operation to be performed in 

 the sanctuary itself The Thebes temple on this hypo- 

 thesis assured this — and at the winter solstice. 



The next explanation I submit to Egyptologists with 

 much fear and trembling. It is, briefly, that about 

 3200 B.C. observations of the star Sirius replaced, or 

 were added to, those made of y Draconis. Mythologically 

 a new I sis would be born. 



I base this suggestion on the following considera- 

 tions: — 



(i) While the Denderah Hathor was represented by 

 the disk and horns on a hippopotamus ; at Thebes, the 

 city of the " Bull " Amen, Hathor is represented by a 

 cow with a like headdress. 



(2) Sirius, represented originally as a goddess with the 

 two feathers of Amen standing in a boat, is now changed 

 to a cow with the disk and horns. 



(3) Hathor was the cow of the western hills of Thebes. 

 It is in these hills that the temple Der el-Bahari lies, 

 and this temple if oriented originally to Sirius would have 

 been founded about 3000 B.C., when Sirius would have 

 an amplitude of 26°. 



Fig. 4.— The cow Hathor appearing from the western hills of Thebes. 



(4) A temple was built in later times at Denderah 

 oriented to Sirius, and Sirius with the cow's horns and 

 disk became the great goddess there, and when her 

 supremacy all over Egypt became undoubted, her birth- 

 place was declared — at Denderah— to have been Den- 

 derah, ^ 



(5) In the month list at the Ramesseum the first 

 month is dedicated to Sirius, the third to Hathor. 

 This is not, however, a final argument, because local 

 cults may have been in question. 



(6) Set seems to have been a generic name applied to 

 the northern ( .? circumpolar) constellations, perhaps be- 

 cause J(?/= darkness, and these stars, being always visible 

 in the night, may have in time typified it. Taurt, the 

 hippopotamus, was the wife of Set. The Thigh was the 



' Brugsch thus translates one of the inscriptions :— " Horus in weiblicher 

 Gestalt ist die Furstin. die Machtige, die Tnronfolgerin und Tochter eines 

 Thronfolger. Ein fliegender Kafer wird (sie ?) geboren am Himmel in der I 

 uranfanglichen Stadt (Denderah) zur Zeit der Nacht des Kindes in seiner i 

 Wiege. Es strahit die Sonne am Himmel in der Dammerung, wann ihre 

 Geburt voUbracht wird." — Brngsch, ' Astron. Inscription.," p. 97. I 



thigh of Set, &c. y Draconis was associated therefore 

 with Set, and the symbolism for Set-Hathor was the 

 hippopotamus with horns and disk. Now, if, as is sug- 

 gested, Sirius replaced y Draconis, and the cow replaced 

 the hippopotamus, the cult of Set might be expected to 

 have declined ; and as a matter of fact the decline of the 

 worship of Set, which was generally paramount under 

 the earlier dynasties, and even the obliteration of the 

 emblems on the monuments, are among the best-marked 

 cases of the kind found in the inscriptions.^ 



(7) The Isis temples of Denderah were certainly 

 oriented to Sirius ; the Hathor temple was as certainly 

 not so oriented. And yet, in the restorations in later 

 times (say Thotmes III.— Ptolemies), the cult has been 

 made Sirian, and the references are to the star which 

 rises at the rising of the Nile. 



I do not see why the Egyptians should have hesitated 

 to continue the same cult under a different star when 

 they apparently quite naturally changed Orion from a 

 form of Osiris (Sah-Osiris) and a mummy (as he was re- 

 presented when the light of his stars was quenched at 

 dawn at the rising of Sirius) to that of Sah- Horus (when 

 in later times the constellation itself rose heliacally). 



J. Norman Lockyer. 



NO. 



1164. VOL. 45I 



SUPERHEATED STEAM. 



T HAVE noticed a curious misapprehension, even on 

 •*■ the part of high authorities, with respect to the 

 application of Carnot's law to an engine in which the 

 steam is superheated after leaving the boiler. Thus, in 

 his generally excellent work on the steam-engine,- Prof. 

 Cotterill, after explaining that in the ordinary engine the 

 superior temperature is that of the boiler, and the inferior 

 temperature that of the condenser, proceeds (p. 141) : 

 " When a superheater is used, the superior temperature 

 will of course be that of the superheater, which will not 

 then correspond to the boiler pressure." 



This statement appears to me to involve two errors, 

 one of great importance. When the question is raised, 

 it must surely be evident that, in consideration of the high 

 latent heat of water, by far the greater part of the heat is 

 received at the temperature of the boiler, and not at that 

 of the superheater, and that, of the relatively small part 

 received in the latter stage, the effective temperature is 

 not that of the superheater, but rather the mean between 

 this temperature and that of the boiler. An estimate of 

 the possible efficiency founded upon the temperature of 

 the superheater is thus immensely too favourable. Super- 

 heating does not seem to meet with much favour in prac- 

 tice ; and I suppose that the advantages which might 

 attend its judicious use would be connected rather with 

 the prevention of cylinder condensation than with an 

 extension of the range of temperature contemplated in 

 Carnot's rule. 



If we wish effectively to raise the superior limit of 

 temperature in a vapour-engine, we must make the boiler 

 hotter. In a steam-engine this means pressures that 

 would soon become excessive. The only escape lies in 

 the substitution for water of another and less volatile fluid. 

 But, of liquids capable of distillation without change, it is 

 not easy to find one suitable for the purpose. There is, 

 however, another direction in which we may look. The 

 volatility of water may be restrained by the addition of 

 saline matters, such as chloride of calcium or acetate of 

 soda. In this way the boiling temperature may be 

 raised without encountering excessive pressures, and 

 the possible efficiency, according to Carnot, may be 

 increased. 



The complete elaboration of this method would in- 

 volve the condensation of the steam at a high tempera- 



■ Rawlinson, vol. i., p. 317 ; vol. ii., p. 347 ct seq. 

 '•' Second edition (Spon : London, 1890). 



