A LESSON IN OBSERVATION
The strenuous work was completed before night covered the scene. The
flying machines had acted as a screen, and the guns, now in position,
were effectually covered from the eyes of a prying foe. As they were
about to leave the captain said:
"For the present you may find room in the vans, but tomorrow the
regular quarters will be prepared near the guns."
The steaming hot supper, which was brought up in the kitchen vans, was
relished as never before. After the meal they sat around and talked
over the incidents of the day, and learned each other's histories, for
there is a comradeship in the field that obtains nowhere else in any
other occupation.
"And so you have been flying?" said the sergeant. "That has always had
a fascination for me, but, strange as it may seem, I have never yet
been up in the air, although I have had many opportunities. I have
often wondered how things look from a height of two kilometers."
"Well, the first time I went up I couldn't distinguish a thing," said
Ralph. "I could tell what trees were, and could make out rivers, and
houses, of course, but outside of that everything else looked like a
blurred picture."
"Couldn't you make out people walking, or troops marching, and the
like?" asked one of the men.
"No, indeed," said Alfred. "Why, how big do you suppose a man would
look at a distance of five thousand feet, when you are directly
overhead?"
"I don't know," replied the sergeant, with an inquiring look. "I don't
suppose he could be seen at all, unless he happened to be moving."
"Why, at that distance it would be impossible to see the man, moving
or not, for he would not appear bigger to the eye than the end of the
finest wire," Ralph informed him.
"I remember when we made our first flights at Bar-le-Duc, that the
lieutenant asked us to give him our impression as to the sizes of
objects we saw and to tell him what they were. When a fellow is
flying about the first thing he will notice is a river, if there is
one anywhere in the neighborhood, and, of course, I saw a bridge. I
couldn't wait until we landed before I marked it down on a piece of
paper: 'A bridge; 200 feet long.' I thought I'd get it long enough. We
were then flying about 5,000 feet above the earth. I saw the lieutenant
smile. At that height the bridge looked about like a lead pencil held
ten feet from the eye. Well, when we landed, the lieutenant said: 'It
was a bridge, sure enough, but it happens to be seven hundred feet
long.'"
"That reminds me," observed Alfred, "that we talked about several
other things on that trip, and it will show how poor the judgment
is unless the eye is well trained. Do you remember the drill ground
east of Fleury? Well, we were asked to put down the number of men we
could estimate in each group, and I was particularly anxious to tell
the lieutenant how many men were in each of the squares which were
formed. Each block of men, as they appeared to me, were about the size
of a domino. I felt sure there couldn't be more than 50 men, but the
lieutenant said there were at least two hundred."
"But that isn't the worst of it," rejoined Ralph. "We knew they were
soldiers, because they were on the drill ground, but if that same
number of men had been in the open country, it would have taken an
expert to see them. I was fooled in that way not long after the
experience I was just telling about, and, although the lieutenant
pointed out the marching men, I couldn't spot them until he told me to
watch for the glint of steel that would occasionally flash out. Then I
understood."
"I have heard it said that if every moving object, it mattered not how
big it might be, were painted the same color as the earth and other
surrounding objects, aviators would not be able to discover them; is
that really so?" inquired the sergeant.
"Yes," answered Ralph. "I think it's pretty near the truth. Sometimes
even the upturned face of a man will attract attention, although the
face makes a mighty small speck, but I believe that fellows who think
they can see a man's face at a distance of 5,000 feet, either use a
field glass, or the man below happened to be wearing eye glasses, for
they make fine reflectors for the airmen."
"But those who are flying get birds' eyes, after a time," said Alfred.
"What is that?" asked the captain, who appeared at the door. "Do you
think a man's eyesight grows keener by flying, after he is at it for a
time?"
"It seems so to me," answered Ralph.
The captain shook his head. "I think that is a misapprehension. The
eyesight does not become sharper or more acute."
"Then how is it that I can now see things that I could not notice when
we first began to fly?" asked Alfred.
"Observation! observation, my boy! You can't see one whit better today
than you could the first time you went aloft," said the captain. "The
eye is a very deceptive thing,—you laugh at the statement,—well,
I'm going to prove it. In everything you see the judgment is not
formed by what the eye tells you, but by your knowledge, your habit of
observation and application growing out of previous experiences."
"Pardon me, Captain. Do you mean to say that the eye doesn't correctly
tell you distance or size or what the object really is?" asked Alfred.
"That's exactly what I mean," replied the captain.
"Well, that's a new idea to me," said Ralph.
"Suppose we examine that. I have an article here,—a box, in my hand.
Tell me, Ralph, how large it is, what it is made of, and what it is
used for?" said the captain.
"Quite easy," replied the boy. "It is about two inches long; is made of
metal, of some kind, and is used to hold matches."
"The answer needs examination. Now, tell me, first, how you judged it
to be two inches long," remarked the captain.
"Why, I should easily judge that, because it wasn't as big as your
hand, and not even as long as one of your fingers," said Ralph.
"In other words, you used my hand to measure it by, or, if my hand
hadn't been there you would have guessed its size because you knew,
approximately, the size of match boxes; is that it?" asked the captain.
"Yes," was the answer.
"Very well; how did you know it was of metal?" was the next question.
There was a broad grin on the faces of all; that was too easy; Ralph's
face was all aglow as he answered: "Because I know that all match boxes
are made of metal, and it looked like metal."
"You mean it was your previous knowledge; that is a fair answer,"
replied the captain. "But how did you know its uses?"
Ralph glanced about preparatory to making the answer, and Alfred
replied: "I should say because I know that a box of that kind and
of that size, and I've seen hundreds of them, is used for holding
matches."
"Well answered. Now, let us sum up: the eye told you that the box was
about two inches long. That is fairly accurate. You got the measurement
simply by comparison. If a box had been placed within the range of your
vision, so that there would be absolutely nothing with which to compare
it, you could not have told by a mere observation of the eye whether it
was an inch or three inches long," observed the captain.
"Do you mean I wouldn't have been able to tell the size of a match
safe?" asked Alfred.
"No; I didn't say match safe. I said if _a box_ had been exhibited
before you. If I had asked you the size of a match safe it wouldn't
have been necessary for me to exhibit it; your knowledge of the general
sizes of match safes would have enabled you to answer me without even
glancing at it. Isn't that true?" asked the captain.
"I see what you mean now," said Ralph. "It is previous knowledge that
aids the eye."
"That is the idea," said the captain. "Now, proceed with the next
question. Why did you say it was made of metal?"
"Because I never saw a match safe that wasn't made of some kind of
metal," said Ralph.
"Did the eye tell the truth?" said the captain, taking out his knife and
opening it. "You will see it is made of _papier mache_, merely colored
to look like metal. The eye was a gay deceiver; don't you think so?"
This was too much for the men; there was a sally of laughter in which
the boys joined with the greatest glee.
"But we are not through with this investigation. We have been talking
about a match safe. The sergeant here is a very wise person, and has
had a fine education, so I am going to ask him whether it looks like a
match safe," said the captain.
"I should say so; that is about the only thing that occurs to me," he
answered.
"Are you relying on your eyes, or what?" asked the captain.
"Well,—on my eyes and on my previous knowledge," answered the sergeant.
"Then you are doubly wrong," said the captain, as he opened the lid,
and exposed the interior of the case filled with tablets. "It is not
a match safe; was never intended for one, and was never used for that
purpose. Have I proven my case?"
The company applauded the clever manner in which the captain explained
the subject.
"This leads me to say that the eye brings into your range something
which may be familiar, that is, something of which you have seen
before, and you say you have seen thus and so; or, on the other hand,
you see something which is unknown, or strange. It is at this point
where the value of observation is of service. If you cannot compare its
size with something you have knowledge of, or have no gauge by which
you can determine of what it is made, and no means which will enable
you to judge of its use, or its purpose, you must depend on your own
judgment to decide what it can possibly be. In course of time the man
in an airship becomes a thinker and a reasoner, and does not depend so
much on the eye, as upon a judgment aside from that which the eye tells
him. Do you understand now what I mean when I say that the eye does not
grow more acute, but that the mind becomes more active, and, through
observation, enables the aviator to judge more accurately as time goes
on."
The captain's argument was unanswerable. It was a revelation to the
boys, and, as the captain was about to leave, Ralph said: "We thank
you, Captain, for the wonderful lesson you have taught us. I am sure we
shall never forget it, and I know we shall profit by it."