Chapter IX in Earth not a Globe
Somewhat the dimensions in this chapter seem not to match:
According chapter V the hight of the sun above the surface is given as at least 700 miles.
Now the first analogy given, is a row of lamp posts some 3 meters high.
A diagram with the sun shown above a church is given, placing the sun about 3 times the hight of the church... 700 miles??
And another with a tunnel. what do you estimate the hight of the tunnel, 700 miles??
The reason given for sunrise/set is "Law of Perspective".
http://www.sacred-texts.com/earth/za/za27.htm
ALTHOUGH the sun is at all times above the earth's surface, it appears in the morning to ascend from the north-east to the noonday position, and thence to descend and disappear, or set, in the north-west. This phenomenon arises from the operation of a simple and everywhere visible law of perspective.
http://www.sacred-texts.com/earth/za/za32.htm
Law of Perspective
The smallest angle under which an object can be seen is upon an average, for different sights, the sixtieth part of a degree, or one minute in space; so that when an object is removed from the eye 3000 times its own diameter, it will only just be distinguishable;
The "object" which has to be receded into the vanishing point, is the hight of the sun above the ground.
Or think about - to stay with the first analogy - lamp posts 700 miles high.
So the distance, where the sun recedes into the horizon is 3000 * 700 miles --- 2,100,000 miles.