1850 S. Judd xxii. 250 My teacher..used to instruct us that there was an earth-line of the sky, as well as a sky-line of the earth.
1907 R. Kipling (1918) 2 They are concerned with matters hidden—under the earth-line their altars are.
1952 N. Nicholson in C. Dyment 63 A day with sky so wide, So stripped of cloud..that you can see The earth-line as a curve.