304 OF THE DISTANCES AND MAGNITUDES

the earth’s distance be only bvs, than if it beB V S.

This being properly understood, let us nowsuppose the earth to be transparent, like glass,and that a person was placed at the center C,(fig. 3.) and kept looking at the fun S, duringthe time in which Venus moves in her orbitfrom F to /, through the space F GY gf. Inthis cafe the earth’s motion on its axis couldhave no effect on his position, because it couldnot carry him away from the point C ; andtherefore when Venus is at F, in her orbit, shewould appear to be just within the fun’s surface,touching his eastern edge at K, at her first in-ternal contact with him; and as she moves onfrom F to /, in her orbit, she would appear topass over the fun, from K to L, in the line K kL, which is called the line of her transit overthe fun. And when fire is at f, in her orbit,file would appear to be just beginning to leavethe fun’s western edge at L, at her last internalcontact with him. So that if Venus could beseen from the earth’s center C, fire would movefrom F to f, in her orbit, in the time fire wouldappear to move from K to L on the fun, orfrom her first internal contact to her last.

This being the appearance of the transit at theearth’s center, let us now suppose, that an ob-server is placed on the earth’s surface at a, andthat he is carried from æ to b, by the motion of

the