The Scientific American Boy; Or, The Camp at Willow Clump Island

quarters was to make a complete survey of Willow Clump Island and its

eying In

nches wide. In the center we sawed out a circular opening

er 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

g 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 exac

it L

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

Tr

The Tri

n pin projecting from its center adapted to engage the hole in the circular pi

e 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 t

ed a good-sized sinker to its lower end. In connection with this plumb line we occasionally used a pro

t edge of this protractor against the base of the tripod, and noting the number of degrees between the 90 degree

yor's

he Surveyo

andard surveyor's link. The wire we used was No. 16 galvanized iron, which was rather stiff and difficult to bend.

enters. 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

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 si

rveyor

Cutting O

od about 6 feet long. A target or sighting disk was mounted on the stick. This d

e 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 t

t, 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 th

Method of

le Ed devised a very simple method by which we could de

akes with the other two sides," said Uncle Ed, "I'll tell you the length of t

of Our First Le

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 ba

s. 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

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

ard. 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 qu

g the

e 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 call