If I use that part of the brass circle which is occupied by our present pole-star, we get the apparent revolution of the heavens with the earth's axis pointing to the pole-star of to-day. If we wish to investigate the position of things, say 8,000 years ago, we bring the globe back again to its bearings, and then adjust the screws into the holes in the brass circles which are proper for that period. When we have the globe arranged to 6000 years B.C. (_i.e._, 8,000 years ago), in order to determine the equator at that time all we have to do is to paint a line on the globe-in some water-colour, by holding a camel's-hair pencil at the east or west point of the wooden horizon. That line represents the equator 8,000 years ago. Having that line, of course, the intersection of the equator with the ecliptic will give us the equinoxes, so that we may affix a wafer to represent the vernal equinox. Or if we take that part of the ecliptic which is nearest to the North Pole, and, therefore, the N. declination of which is greatest, viz., 23½° N., we have there the position of the sun at the summer solstice, and 23½° S. will give us the position of the sun at the winter solstice. So by means of such a globe as this it is possible to determine roughly the position of the equator among the stars, and note those four important points in the solar year, the two equinoxes and the two solstices. I have taken a period of 8,000 years, but I might just as easily have taken a greater or a smaller one. By means of this arrangement, therefore, we can determine within a very small degree of error, without any laborious calculations, the distance of a star north or south of the equator, _i.e._, its declination, at any point of past or future time. The positions thus found, say, for intervals of 500 years, may be plotted on a curve, so that we can, with a considerable amount of accuracy, obtain the star's place for any year. Thus the globe may be made to tell us that in the year 1000 A.D. the declination of Fomalhaut was 35° S., in 1000 B.C. it was 42°, in 2000 it was about 44°, in 4000 it was a little over 42° again, but in 6000 B.C. it had got up to about 33°, and in 8000 B.C. to about 22°. The curve of Capella falls from 41° N. at 0 A.D. to 10° at 5500 B.C., so we have in these 5500 years in the case of this star run through a large part of that variation to which I have drawn attention. I have ascertained that the globe is a very good guide indeed within something like 1° of declination. Considering the difficulty of the determination of amplitudes in the case of buildings, it is clear that the globe may be utilised with advantage, at all events to obtain a first approximation. CHAPTER XIII. THE EGYPTIAN HEAVENS--THE ZODIACS OF DENDERAH.