Page:Popular Astronomy - Airy - 1881.djvu/167

miles. Let Figure 44 be a perspective view of the state of things in which the sun's distance is supposed

Fig. 43.

to be fifty millions of miles, and its breadth to be half-a-million of miles. In Figure 43 the distance of Venus from the sun must be seventy-two millions

Fig. 44.

of miles; but in Figure 44, the distance of Venus from the sun is only thirty-six millions of miles. Of all these measures we do not know anything absolute, we only know their proportions.

But there is one measure which we do know