58 



NATURE 



[May 21, 1891 



preservation that the Germans, in the year 1844, could 

 give us an infinite number of details about it, and locate 

 the position of the innumerable courts. Its orientation 

 to the solstice we can claim as an early astronomical 

 observation. So it is quite fair to say that, many thousand 

 years ago at all events, the Egyptians were perfectly 

 familiar with the solstices, and therefore more or less 

 fully with the yearly path of the sun. 



But so far we have only dealt with solstices. Did 

 the Egyptians know anything about the equinoxes 1 

 Certainly. Nothing is more remarkable than to go from 

 the description and the plans of such temples as we have 

 seen at Abydos and Karnak to regions where, apparently, 

 the thought is totally and completely different, such as 

 we find on the Pyramid Plains at Ghizeh ; the orienta- 

 tion lines of the German surveyors show, beyond all 

 question, that these structures are just as true to the 

 sun-rising at the equinoxes as the temples at Abydos and 

 Karnak were to the sun-rising and setting at the solstices, 



Map of British Isles showing the magnetic variation.' 



and the Sphinx was merely a mysterious nondescript sort 

 of thing which was there watching for the rising of the sun 

 at an equinox, as the Colossi of the plain at ThebeB were 

 watching for the rising of the sun at the winter solstice. 



The observations which have been made in Babylonia 

 are very discordant among themselves, and at present 

 it is impossible to say, from the monuments in any of 

 this region along the Euphrates valley, whether the 

 temples indicate that the solstices were familiar to the 

 Babylonians ; but no doubt some of the temples were as 

 perfectly squared to the equinox as some walls at Memphis 

 or the Pyramids at Ghizeh ; and certainly there is no 

 doubt that as early as Solomon's time the temple at 

 Jerusalem was orientated to the east with care. We find 

 there that the direction of the axis of the temple shows 

 the existence of a cult connected with the possibility of 



' For Figs. 11-13 I am indebted to the kindness of Mr. Stanley, Great 

 Turnstile, Lincoln's Inn Fields. 



NO. 1 125, VOL. 44] 



seeing the rising of the sun on the day of an equinox, 

 possibly at the time which we now call Easter. 



All the doors being opened, the sunlight would pene- 

 trate over the high altar, where the sacrifices were offered, 

 into the very Holy of Holies, which we may remember was 

 only entered by the High Priest once a year. 



Have we any other evidence except the evidence 

 afforded by temples ? Yes. It has been stated that we have 

 no temple evidence from China, but there is a good deal 

 of written evidence, and there is no doubt that in China 

 the solstices and the equinoxes were perfectly well known 

 1 100 years B.C. Was it difficult to obtain this knowledge ? 

 Did it indicate that the people were great astronomers ? 

 Nothing of the kind ; nothing is so easy as to determine a 

 solstice or an equinox. 



We know from the Egyptian tombs that their stock-in- 

 trade, so far as building went, was very considerable ; 

 they had squares, they had plumb-lines, they had scales, 

 and all that sort of thing just as we have. Suppose an 

 Egyptian wished to determine the time of an 

 equinox. He would first of all make a platform 

 quite flat ; he could do that by means of the square 

 or plumb line ; then he would get a ruler with 

 pretty sharp edges (and such rulers are found in 

 their tombs), and in the morning of any day he 

 would direct this ruler to the position of the sun 

 when it is rising and he would draw a line ; he 

 would do the same thing in the evening when the 

 sun set ; he would bisect the angle made by these two 

 lines, and it would give him naturally the north 

 and south points, and a right angle to those would 

 give him the east and west. So that from obser- 

 vation of the sun on any two days in the year he 

 would practically be in a position to determine 

 the position at which the sun would rise and set at 

 the equinox. 



There is another way of doing it. Take a 

 vertical rod. Suppose that the sun is rising, let 

 the rod throw a shadow ; mark the position of the 

 shadow ; at sunset we again note where the 

 shadow falls. If the sun rises exactly in the east 

 and sets exactly in the west, those two shadows 

 will be continuous and we shall have made an 

 observation at the absolute equinox. But suppose 

 the sun not at the equinox, a line joining the ends 

 of the shadows equally long before and after noon 

 will be an east and west line. 



It is true that there may be a slight error unless 

 we are very careful about the time of the year at 

 which we make the observations, because when 

 the sun is exactly east or west at the time of rising 

 or setting it is moving most rapidly. So it is 

 ____^ better to make the above observations of the sun 

 nearer the solstices than the equinoxes, because 

 the sun changes its declination most quickly at the 

 equinoxes. 

 Such a rod as this, which I may state is sometimes 

 called a gnomon, may be used with another object in 

 view : we may observe the length of the shadow cast by 

 the sun when it is lowest at the winter solstice, and when 

 it is highest ; at these two positions of the sun obviously 

 the lengths of the shadows thrown will be different. When 

 the sun is nearest overhead in the summer the shadow 

 will be least, when the sun is most removed from the 

 vertical the shadow will be longest. 



The day on which the shortest shadow is thrown at 

 noon will define the summer solstice ; when the shadow is 

 longest we shall have the winter solstice. 



This in fact was the method adopted by the Chinese 

 to determine the solstices, and from it very early they 

 found a value of the obliquity of the ecliptic. 



It may be said that it is only a statement, and that the 

 record has been falsified ; some years ago anyone who 

 was driven by facts to come to the conclusion that any 



