Chapter 32

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.

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.

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.

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.

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:

"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.

"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.