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----"

"Lieutenant Tibbetts," said Hamilton in ponderous reproof, "you are
behaving very strangely."

"Look here, dear old Ham," wheedled Bones "can't you pretend you asked
me what a Vertical Interval was?"

Hamilton reached round to find something to throw, but this was
Sanders's study.

"You have a criminal mind, Bones," he said helplessly. "Now get on with
it. What are 'Hachures'?"

"Hachures?" said Bones, shutting his eye. "Hachures? Now I know what
Hachures are. A lot of people would think they were chickens, but I
know ... they're a sort of line ... when you're drawing a hill ...
wiggly-waggly lines ... you know the funny things ... a sort of...."
Bones made mysterious and erratic gestures in the air, "shading ...
water, dear old friend."

"Are you feeling faint?" asked Hamilton, jumping up in alarm.

"No, silly ass ... shadings ... direction of water--am I right, sir?"

"Not being a thought-reader I can't visualize your disordered mind,"
said Hamilton, "but Hachures are the conventional method of representing
hill features by shading in short vertical lines to indicate the slope
and the water flow. I gather that you have a hazy idea of what the
answer should be."

"I thank you, dear old sir, for that generous tribute to my grasp
of military science," said Bones. "An' now proceed to the next
torture--which will you have, sir, rack or thumbscrew?--oh, thank
you, Horace, I'll have a glass of boiling oil."

"Shut up talking to yourself," growled Hamilton, "and tell me what is
meant by 'Orienting