372- 



NA TURE 



[August 17, 1893 



ilferoiO 



Cult. 



Pyramid i6 

 Pyramid 20 



Magnetic 

 .\zitnuth. 



N. 102 E. 

 N. 103 E. 



Astron Jinical -p. 

 Amplitude. 



sl S. of E, S. 



^J S. of E. I S. 



3k 

 4i 



Temple near Wasser 



Becken N. 112 E. 



Pyramid 15 N. 112 E. 



Pyramids 14, 37 ... 1 N. 113 E. 



134 S. of E. 

 13* S. of E. 

 14I S. of E. 



Pyramid 10 

 Pyramid 39 



Pyraaiid 19 



N. 116 E. 

 N, 118 E. 



S. 123 

 S. I2i 



174 S. ofE. S. i6a 

 19J S. ofE. '• S. iSf 



N. 83 E. ' 154. N. of E. i N. 143 



Nm-i.'^ 



APPARATUS ILLUSTRATING MICHELSOA'S 

 METHOD OF OBTAINING INTERFERENCE 

 BANDS. 



IN the American Journal 0/ Science (or Augnsi, i^Zl, 

 Captain Michelson described an ingenious method 

 for producing interference bands, used by him in deter- 

 mining the relative motion of the earth and the lumini- 

 ferous ether. Light from a lamp at a falls on a thinly 

 silvered mirror b, where it divides into two rays — one, be, 

 reflected from the thinly silvered surface, is reflected 

 back to b by the plane mirror c ; the other ray traverses 

 the glass plate b, and falls on the plane mirror d, whence 

 it is reflected back to b. Here both rays reunite, and 

 pass onward towards. The mirrors n'and care silvered and 

 polished on their front surfaces. By this means bands, 

 similar to Newton's rings, are obtained between the mirror 

 c and the reflection of rf in b; the retardation of one ray 

 with respect to the other being the \engi\\bc-bdj f\i an un- 

 silvered piece of plane glass, cut from the same piece as^, 

 and placed in the ray b e, so as to compensate for the ray b d 

 passing twicethroughi^ ; otherwise, owing to the dispersive 

 power of the glass in b different wave-lengths of light in the 

 ray b d would be unecjually retarded in comparison with 

 the same wave-lengths in the ray b c. If the path 1^ ir be 

 now equalised in length with the path b d, and if, njore- 

 over, the piece of glass/ be exactly equal and parallel 

 with b, the central band will be black, owmg to the ray 



It seems quite justifiable from the above facts to con- 

 clude that the pyramids and temples oriented S.E. and, 

 as I hold, to a Centauri when it heralded the autumnal 

 equinox, were not built by people having the same 

 astronomical ideas, worships, and mythology as those 

 who built at Gizeh due E. and W., and marked the 

 autumnal equinox by the heliacal rising of Antares.'' The 

 only thing in common was noting an equinox, and so far 

 as this goes we may infer that neither people dwelt 

 originally in the Nile Valley, but came by devious ways 

 from a country or countries where the equinoxes had 

 been made out. J. Norman Locryer. 



1 For plans see " Lepsius," vjl. ii. 133 ani 134. \ west variation of 

 8J° has been assumed. 



- For plans see *■ Leps^ui," vol. ii. 130. A west variation of Si has been 

 assumed. 



■5 For plans see " Lepsius," vol. ii. 125 and 127. A west variation of 

 ZY has been assumed. 



^ There is a p jint oT great interest he^e It w)uld seen from C.iptain 

 Lyons' e.vaminati )n of the temples at W.id/ Haifa, which I make out Ij 

 have been orien'.ed to a Centauri, that when the two races were amalga- 

 mated in later times, b^th the stars to waich> I have refsrrej as heralding 

 the equino.x were personified by the saTie goddess Selk 



NO. 1242, VOL. 48] 



d b being reflected from the rarer medium, whilst a b is 

 reflected from the denser medium. 



Apparatus to show these bands can be easily and 

 cheaply set up, and owing to the fact that an extended 

 source of light may be used, they can easily be projected, 

 and thus many interesting experiments shown to a large 

 audience. The following is a description of a simple 

 construction of the apparatus which I have found to work 

 admirably. 



."Ml the parts are mounted on a piece of plate-glass 

 .J" X 9" X 12". The two mirrors d<\.x\&. c, each two inches 

 square, were silvered by the milk-sugar process, and after- 

 wards polished with washleather and rouge in theordinary 

 manner. The mirror b was withdrawn from the silvering 

 solution when only a thin layer had been deposited ; no 

 polishing was necessary. The layer of silver should re- 

 flect considerably more than half the light incident upon 

 it, as thus the reflections from the unsilvered surface of 

 b become relatively insignificant. Ordinary piate-glass 

 was used in each instance. 



Each mirror was attached vertically by pitch to a stand 

 composed of two pieces of band brass soldered together 

 at right angles, having three feet a, b, c (Fig. 2). In the 

 case of the glasses /',/, and c (Fig. i), a screw of pitch 

 ^5" was inserted in c (Fig. 2) as a rough adjustment for 

 verticalitv of the mirror. 



