[26], l. 2, for “land,” read “level.”

[27], l. 1, for “at the place,” read “at the right place.”

[28], l. 29, for “reconnoitre,” read “reconnoissance.”

[30], l. 3, for “A c d B,” read “A C D B.”

[32], l. 2, the point m in the cut, is one whole division above C; it should be only three fourths of a division.

[38], l. 10 from bottom, for “276,” read “268.”

[39], l. 10 from bottom, for “142.13,” read “143.13”; and last line, for “58.46,” read “48.46.”

[40], l. 7, for “10310,667,” read “10,277,333.”

[42], l. 9, for “Thus,” read “These.”

[42], l. 8 from bottom, for “2°.81 or 2° 48′.6” read “2°.86 or 2°.51.6.”