SURVEYING.
One of the first things we did after getting fairly settled in our new
quarters was to make a complete survey of Willow Clump Island and its
immediate surroundings. Our surveying instruments were made as follows:
THE SURVEYING INSTRUMENT.
[Illustration: Fig. 71. Baseboard of the Surveying Instrument.]
[Illustration: Fig. 72. Sighting Blocks on the Baseboard.]
Out of a 1-inch board we cut a base 15 inches long and 4 inches wide. In
the center we sawed out a circular opening of about 3 inches diameter
and covered this at the bottom by a circular piece 1 inch thick and 5
inches in diameter, thus forming a socket in which our compass fitted
snugly. A hole 1 inch in diameter was drilled through the center of this
circular piece to receive the pivot pin of a tripod. Across each end of
the baseboard we secured a block 4 inches long, 2 inches wide and 1 inch
thick. A 1-inch sight hole was drilled through each block at its center.
A ring of cardboard, on which Uncle Ed marked with radial lines the 360
degrees of the circle, was placed over the compass socket, with the zero
and 180 degree marks pointing toward the sight blocks. The outer faces
of the end blocks were now wet with mucilage and a hair was stretched
vertically across the center of each sight hole. The hairs were then
adjusted by sighting through the holes and moving the nearer hair
sidewise until it was exactly in line with both the zero and the 180
degree marks on the cardboard. Then a hair was stretched horizontally
across the center of each sight hole. Great care was taken to place the
hairs at exactly the same height above the baseboard. To protect the
hairs after they were adjusted, they were covered with a piece of glass,
which was secured in place by tacks driven into the wood with their
heads projecting over the edges of the glass.
SPIRIT LEVELS.
From one of his pockets Uncle Ed produced two small bottles, the kind
used for holding homeopathic pills. These he filled nearly to the top
with water, corked them and wedged them into grooves cut lengthwise in
the baseboard at opposite sides of the cardboard ring. These grooves
were filled with putty, and to make sure that the bottles were level
with the baseboard the latter was floated on a bit of quiet water and
the bottles were pressed down at one end or the other until the bubble
within rested at the exact center.
THE TRIPOD.
[Illustration: Fig. 73. The Tripod Head.]
[Illustration: Fig. 74. The Tripod Leg.]
[Illustration: Fig. 75. The Surveying Instrument Complete.]
[Illustration: Fig. 76. The Protractor.]
The tripod head was formed of a wooden disk 5 inches in diameter, with a
wooden pin projecting from its center adapted to engage the hole in the
circular piece above referred to. To the bottom of the tripod head were
nailed three blocks 2 inches long and 1 inch square in cross-section.
The tripod legs were made of light strips of wood, 3/8 inch by 1 inch by
5 feet long, which we secured from one of the mills at Lumberville. Each
leg was formed of two of these strips, nailed securely together to
within 20 inches of the top. At the upper ends the strips were spread to
receive the blocks on the tripod head. In this position they were held
by headless wire nails driven into the ends of the blocks and fitting
into holes drilled in the strips. For a plumb line we tacked a cord to
the center of the tripod head, and attached a good-sized sinker to its
lower end. In connection with this plumb line we occasionally used a
protractor consisting of a semicircle of cardboard 5 inches in diameter,
on which the degrees of the circle were marked off with radiating lines,
as illustrated in Fig. 76. By holding the straight edge of this
protractor against the base of the tripod, and noting the number of
degrees between the 90 degree mark and the plumb line, we could tell at
a glance at what angle from the horizontal the instrument was tipped.
SURVEYOR'S CHAIN.
[Illustration: Fig. 77. The Surveyor's Chain.]
[Illustration: Fig. 78. Forming the Links.]
[Illustration: Fig. 79. A Double-Ringed Link.]
We made a surveyor's chain of wire links, each 12 inches long, instead
of 7.92 inches, which is the length of a standard surveyor's link. The
wire we used was No. 16 galvanized iron, which was rather stiff and
difficult to bend. In order to make all the links of exactly the same
size and shape we used a form, around which they were bent. The form
consisted of a 1-inch board in which two 1/2 inch holes were drilled,
just 11-1/2 inches apart, measured from their centers. An oak pin, 1/2
inch in diameter, was driven into each hole and projected about an inch
above the board. Two blocks of oak were secured to the baseboard, just
before each pin, as shown in Fig. 78. This form gave great satisfaction.
A groove was cut in the side of one of the pins to receive the ring of a
completed link, while the wire was passed through this ring and bent
around the peg to form the ring of the new link. After each link was
formed it was carefully measured, and, if too long, was shortened by
flattening the rings endwise, or, if too short, was lengthened by
pinching together the sides of the rings. There were fifty links in our
chain, and every tenth one was formed with a double ring at the end, so
as to distinguish it from the rest (see Fig. 79).
THE SURVEYOR'S ROD.
[Illustration: Fig. 80. Cutting Out a Disk.]
[Illustration: Fig. 81. The Sighting Disk]
[Illustration: Fig. 82 Nut Fastened in Block.]
We completed our outfit by making a surveyor's rod out of a straight
stick of wood about 6 feet long. A target or sighting disk was mounted
on the stick. This disk was 6 inches in diameter, and was sawed out of a
6-inch square board by making straight cuts across the corners and then
smoothing off the edge to a perfect circle with a draw-knife. The
thickness of the disk was only 1/2 inch. At the back of the disk we
fastened a block of wood with a slot cut in it to receive the rod, as
shown in Fig. 81. To hold the disk at different heights on the rod a
small bolt was used. The nut on this bolt was slipped into a hole on the
block at the bottom of the slot and held in place by driving in nails
about it, as illustrated in Fig. 82. The bolt was then passed through
the hole and threaded through the nut, with its inner end bearing
against the rod. The disk could thus be held at any desired position by
tightening up the bolt. A piece of white paper was now pasted over the
disk. The paper was marked off into quarters, and opposite quarters were
painted black so that it would be easy to sight, from a distance, the
exact center of the target.
A SIMPLE METHOD OF SURVEYING.
Of course, none of us had studied trigonometry, but Uncle Ed devised a
very simple method by which we could determine distances quite
accurately without much figuring.
"If you will tell me the length of one side of a triangle and the angles
it makes with the other two sides," said Uncle Ed, "I'll tell you the
length of the other two sides and the size of the third angle. This is
how I will do it:
[Illustration: Fig. 83. Diagram of Our First Lesson in Surveying.]
"Say the line is 6 inches long and one angle is 35 degrees, while the
other is 117 degrees. Let us draw a 6-inch straight line. This we will
call our base line. Now we will place the base edge of our protractor on
the base line with its center at the right hand end of the line. At the
37 degree mark we will make a dot on the paper so, and draw a line from
the right hand end of the base line through this dot. Now we will do the
same thing at the opposite end, making a dot at 107 degrees from the
line, and draw a line from the left hand end of the base line through
this dot.
"If we extend these lines until they intersect, we will have the
required triangle, and can measure the two sides, which will be found to
be about 12 inches and 8 inches long, and the third angle will measure
just 26 degrees. It doesn't make any difference on what scale we draw
the triangle, whether it be miles, yards, feet, inches or fractions of
an inch, the proportions will be the same. If the base line had been 6
half-inches, or 3 inches long, and the same angles were used, the other
two lines would measure 12 half-inches, or six inches, and 8
half-inches, or 4 inches. If the base line were 6 quarter-inches long,
the sides would be 3 inches and 2 inches long.
[Illustration: Fig. 84. Determining the Distance to the Tree.]
"Now, for example, I am going to measure the distance to that tree over
there. Get out your chain and measure off a straight line 10 feet long.
Now, I'll set the surveying instrument with the plumb-bob right over the
end of this line, and sight through the two sight holes until I bring
the two vertical hairs in line with each other and the tree. Look at the
compass needle. It points to the 173 degree mark on the cardboard ring.
Now, Bill, you hold the rod at the other end of our base line while I
swing this instrument around and sight it. There, the needle points to
92 degrees, and subtracting this from 173 the difference, 81 degrees, is
the angle at the right end of our base line. We'll do the same thing at
the other end of our line. See, the compass needle points to 189
degrees, and now sighting to the pole at the other end of the line we
find that the needle points to 268. The difference, 79 degrees, is
therefore the size of the angle at the left end of our base line. Now we
will draw this out on paper, as we did our first triangle, using
quarter-inches to represent feet. Our base line was 10 feet long, and we
will therefore draw a line 10 quarter-inches, or 2-1/2 inches long, on
our drawing board. On this line we will construct the triangle, using
the angles 81 and 79 degrees. There, that's how our triangle looks, and
the right hand side measures 7-1/4 inches, while the left hand side
measures 7-5/16 inches. That is, 29 quarter-inches for one side and
29-1/4 quarter-inches for the other. As each quarter-inch represents a
foot, you will find that the tree is about 29 feet from the right end of
our base line and 29 feet 3 inches from the left hand end. Of course,
our instrument is not perfect, neither is our drawing; but if you
measure it off with the chain you will see that I am not very far from
correct."
MAPPING THE ISLAND.
Most of our surveying was done by actual measurement, the surveying
instrument being used only to determine the exact direction of the
measurement. However, there were some measurements which we could not
make directly with the chain. For example, we wished to know just how
far it was from our tent to the Jersey shore of the river. We measured
off a base line along our shore 400 feet long and sighted to a point
directly across the river from our tent. The angle in front of our tent
was 90 degrees, and at the other end of the base line was 73 degrees.
When we drew out our triangle on the scale of 100 feet to the inch we
found that the shorter side directly in front of the tent was almost
exactly 13 inches long. This meant that the river at this point was
1,300 feet wide, nearly a quarter of a mile. On the other side of the
island we found, in the same way, that the river at its narrowest point
was about 500 feet wide. This portion of the river we named Lake Placid,
as the water was very still and quite deep. This was due to a sort of
natural dam formed at the lower end of our island. The small island that
Dutchy found was kite-shaped, with a tail of boulders which extended
almost all the way across to a rocky point on the Pennsylvania shore.
The channel between "Kite Island," as we called it, and Willow Clump
Island was not more than fifteen feet wide in some places, and through
this the water swept with a swift current down past a narrow neck of
land to join the main current. This narrow stretch of land we named the
Tiger's Tail, owing to its peculiar shape. It was in the hook at the end
of this tail that we discovered the old bridge wreck above referred to.
From the tip of the Tiger's Tail to Point Lookout, at the extreme upper
end of Willow Clump Island, it was a little under a half-mile. The shore
all along Lake Placid was very steep, except near Point Lookout. At one
place there was a shallow bay which we called the lagoon.