On a certain summer morning, Hamilton sat at the desk, a stern and sober figure, and Bones, perspiring and rattled, sat on the edge of a chair facing him.
The occasion was a solemn one, for Bones was undergoing his examination in subjects "X" and "Y" for promotion to the rank of Captain. The particular subject under discussion was "Map Reading and Field Sketching," and the inquisition was an oral one.
"Lieutenant Tibbetts," said Hamilton gravely, "you will please define a Base Line."
Bones pushed back the hair straggling over his forehead, and blinked rapidly in an effort of memory.
"A base line, dear old officer?" he repeated. "A base line, dear old Ham——"
"Restrain your endearing terms," said Hamilton, "you won't get any extra marks for 'em."
"A base line?" mused Bones; then, "Whoop! I've got it! God bless your jolly old soul! I thought I'd foozled it. A base line," he said loudly, "is the difference of level between two adjacent contours. How's that, umpire?"
"Wrong," said Hamilton; "you're describing a Vertical Interval."
Bones glared at him.
"Are you sure, dear old chap?" he demanded truculently. "Have a look at the book, jolly old friend, your poor old eyes ain't what they used to be——"