The Scientific American Boy Part 11

[Ill.u.s.tration: Fig. 155. The Sight Rod.]

[Ill.u.s.tration: Fig. 156. Nut Set in Baseboard.]

At the end opposite to where the mirror frame was swiveled we mounted a sight rod, which was merely a round stick of wood 1/2 inch in diameter and about 8 inches long. We cut the stick from one of the rounds of an old broken chair. The upper end of the rod was whittled to a point and one side was flattened as shown in Fig. 155. Out of a piece of heavy white cardboard we cut a round disk about 1/4 inch in diameter, with a shank 1 inch long sticking out at one side. This was fastened with a single tack to the flattened end of the rod in such a position that the point lay exactly against the center of the disk. The disk could then be turned up or down, to cover or uncover the point of the rod, as desired.

The rod was fitted snugly into a hole in the baseboard, and could be raised or lowered to any extent desired, but we had to provide some sort of an arrangement for making it stay where it was put. A small hole was drilled from the edge of the baseboard through to the hole in which the rod was fitted. A square socket was chiseled out around the small hole to receive a nut. The nut was firmly wedged in and held in place by driving in nails along the edges. A bolt or machine screw was threaded through the nut, so that its inner end pressed against the sighting rod.

By tightening this screw the rod could be secured at any height desired.

The instrument was mounted on a tripod similar to the one used for our surveying instrument. To this it was attached by means of a bolt, which pa.s.sed through the center of the baseboard and the tripod head.

THE SCREEN.

[Ill.u.s.tration: Fig. 157. Section through Shutter.]

[Ill.u.s.tration: Fig. 158. General View of Screen.]

The screen, or shutter, of the heliograph was mounted on a separate tripod, so as to prevent shaking the mirror when it was operated. It was made something like a window shutter. We cut out two slats, each 2-1/2 inches wide and 6 inches long. They were made of hardwood 3/8 inch thick. The upper and lower edges were tapered down to a thickness of 3/16 inch. Light nails were driven into the slats at the ends, and the nail heads were then filed off so that the projecting ends formed trunnions for the slats to turn on. The slats were linked to a connecting rod with double point tacks. A small double point tack was driven into the upper edge of each slat about 1/2 inch from the right hand end. Then through each of these tacks we hooked a second double point tack and drove it into the rod. The tacks on the rod were placed just 2 inches apart. A substantial frame was then made of 3/4-inch stuff 1-1/2 inches wide. The frame was square, with an opening that measured 6 inches each way, into which the slats were fitted. Before nailing the frame together we drilled holes in the side pieces for the trunnions of the slats to turn in. These holes were just 1-3/4 inches apart. After the slats had been set in place, the frame was fastened together and then nailed to a baseboard, which was fastened by a bolt to the tripod.

The shutter was operated by a key something like a telegraph key. It was made of a narrow stick of wood hinged at one end to the lower strip of the shutter frame, and a spool sawed in two was fastened to the other end to serve as a handle for the key. A string connected the key with the connecting rod. The slats were kept closed by a spring, which was fastened at one end to the connecting rod and at the other to the top of the frame. At first we used a rubber band for this purpose, but it soon wore out, so we then made a spiral spring out of stiff spring bra.s.s wire by wrapping it around a pencil. When the key was pressed down the slats would be turned open, as shown in Fig. 159; but as soon as the key was released the spring would pull them back again.

FOCUSING THE INSTRUMENT.

[Ill.u.s.tration: Fig. 159. The Heliograph in Operation.]

We were now ready to commence operations with our instruments. The heliograph was set up on the ledge at the top of the cliff. First the disk was turned down, uncovering the point of the sighting rod. Then Bill sighted through the unsilvered spot in the mirror and s.h.i.+fted the rod up and down until the tip end came squarely in line with the door of our straw hut, where Jack was seated, notebook in hand, to take down our message. Reddy stood by him with his wigwag flag to answer back. When the instrument was properly sighted the shutter was set up directly in front of it and the sighting disk turned up to cover the point of the sighting rod. Then came the rather troublesome task of focusing the mirror. The mirror reflected a square panel of light, in the center of which there was a small shadow spot made by the unsilvered peep hole.

The object was to get this shadow to fall on the center of the sighting disk. We knew that then the mirror would reflect the sunlight squarely on the straw hut. We found it quite easy to direct this shadow spot to the disk by holding a sheet of paper in front of the mirror six or eight inches away, and following up the spot on the paper until it reached the disk.

HELIOGRAPH SIGNALING.

[Ill.u.s.tration: Fig. 160. Top View, showing position of Mirror and Shutter.]

When at last we succeeded in properly focusing the mirror Bill pressed the key down three times, sending three quick flashes to Jack as a signal that he was ready to begin. Reddy wigwagged back O. K., and then the first heliographic message was sent from the ledge to the island. It was a rather mixed-up message, and kept Jim and Reddy wigwagging back and forth very strenuously to straighten matters out. It was my duty to keep the mirror focused. As the sun moved across the sky the shadow spot would move off the disk, and I had to keep s.h.i.+fting the mirror to bring the spot back where it belonged. We used the International Telegraph Code, which we had been studying every evening for a week, but it was many weeks before we learned how to use it correctly, even slowly. The International Telegraph Code is as follows:

A - B - C -- D - E F - G -- H I J --- K -- L - M -- N - O --- P -- Q --- R - S T - U - V - W -- X -- Y --- Z -- 1 ---- 2 --- 3 -- 4 - 5 6 - 7 -- 8 --- 9 ---- 0 -----

The three short flashes Bill sent represented the letter S, which stood for the word "signal." A was formed by a short flash followed by a long flash; B by a long flash followed by three short ones, and so on. The key was held down three times as long for the long flash as for the short one. We found the best way of learning to send the signals properly was to count 1 for each short flash, and for each pause between parts of the letter, and 3 for each dash and for each pause between letters. Between words we counted 6. Thus, for the letter A the key would be down when we counted 1, up when we counted 2, down while we counted 3, 4, 5, and up while we counted 6, 7, 8, for the pause after each letter. It was rather a confusing code, I admit, but in time we mastered it, all but Reddy and Fred, who never would learn, but instead used the wigwag code, letting a short flash stand for 1, a long flash for 2 and a double long flash for 3.

THE DOUBLE MIRROR INSTRUMENT.

[Ill.u.s.tration: Fig. 161. The Double Mirror Instrument.]

[Ill.u.s.tration: Fig. 162. Top View, showing position of the Two Mirrors and the Screen.]

Our heliographing instrument did excellent service sending flashes from the cliff to the island, but we couldn't make it work very well sending messages from the island to the cliff, because we had to face almost due north, and then the sun was nearly always at our backs and couldn't s.h.i.+ne squarely on the mirror. This led to our building a double mirrored heliograph the following summer. To begin with, we built an instrument which was the exact duplicate of our first heliograph; then, in addition, to fit in the socket of the sighting rod, we rigged up a second mirror, which was mounted in exactly the same way as the first.

The second mirror was called the station mirror, and differed from the other, or sun mirror, in having a small patch of white paper pasted at the center instead of a peep hole. When using this instrument, we set it up so that the station mirror faced the ledge, then by sighting through the hole in the sun mirror at the reflection in the station mirror we could see just what was in focus. The station mirror had to be moved until the patch at its center hid the ledge from view. After that the sun mirror was s.h.i.+fted until the shadow spot fell on the white patch of the station mirror. When once the station mirror was focused, it could be clamped tightly in place by s.c.r.e.w.i.n.g up the trunnion and swivel nuts.

But the sun mirror had to be constantly s.h.i.+fted to keep the shadow on the patch. Another way of focusing the mirrors was to stand behind the instrument with the head close to the station mirror, s.h.i.+ft the sun mirror until the entire station mirror was reflected in it, with the white patch squarely over the unsilvered spot; then still looking at the sun mirror, the station mirror was s.h.i.+fted until the reflection of the distant station was brought squarely in line with the unsilvered spot on the mirror. The station mirror was now firmly bolted and the sun mirror adjusted until the shadow spot fell on the paper patch.

CHAPTER XIV.

ICE BOATS, SLEDGES AND TOBOGGANS.

As our vacation was drawing to a close, we began to make plans for the Christmas holidays. Our previous Christmas vacation had been so completely taken up with preparations for the trip to Willow Clump Island that we had had no time for the trip itself. We resolved this time to have everything ready beforehand, so that we could spend the entire two weeks in solid pleasure. Our skate sails and snow shoes were stored in the attic, ready for use. If we were to make a trip in the snow we would need a sledge, and then, too, we wanted to make an ice boat. It would hardly pay to build these on the island and then cart them home, so it was decided to break up camp a couple of weeks before school commenced.

BREAKING CAMP.

Consequently, on the first day of September we gathered up our belongings, corraled our chickens, packed our goods, and the next day started for home. Mr. Schreiner, in response to a letter from the secretary, came down with a large wagon in which the majority of the things were packed. The rest of our luggage was stowed in the scow and the canoes, and these were towed down the ca.n.a.l, as before. We reached home late in the afternoon, tired and hungry. It was a treat to sit at the table again and eat some of Mother's appetizing dishes. And say, wasn't that pie great, though! My, how ravenous we were! And then a soft, comfortable bed with spotless white sheets and pillow cases. How soundly we did sleep that night! You can just bet we were all glad enough to get back to civilization, though, of course, no one could have dragged out the confession from a single one of us.

THE ICE BOAT.

[Ill.u.s.tration: Fig. 163. The Backbone.]

[Ill.u.s.tration: Fig. 164. Frame of the Ice Boat.]

[Ill.u.s.tration: Fig. 165. Runner Shoe.]

[Ill.u.s.tration: Fig. 166. The Rudder Shoe.]

School commenced on the 20th of September that year, so we hadn't much time to spare. Work was begun immediately on the ice boat. Our first ice boat was rather a crude one. A 2 by 4 inch scantling 14 feet long was used for the backbone of the boat. The scantling was placed on edge, and to lighten it and improve its appearance it was tapered fore and aft from a point 4 feet from the bow end. The thickness of the ends of the backbone was but 2 inches, as shown in Fig. 163. To the under edge of the backbone, 5 feet from the forward end, a crosspiece was nailed. This crosspiece was a 1-inch board 6 inches wide and 9 feet long. Braces were then run from the ends of the crosspiece to the forward and rear ends of the backbone, and at the rear end several boards nailed across the braces served as a seat for the boat.

Our next task was to rig up the runners. For these we used skates, which were so arranged that we could remove them whenever we wanted to. Three blocks of wood were used for the runner shoes. Two of them were cut from a 2 by 4 scantling and measured a foot in length. The third block was only 1 inch thick, but was otherwise of the same dimensions. The skates were laid face downward on the blocks with the clamping levers open; then we marked the places where the clamping jaws touched the wood and drilled holes at these points. The forward end of each block was also tapered off to fit flat against the face of the skate. Then by inserting the jaws in the holes and closing the levers, the skate was clamped to the block, just as it would be to a shoe. The two 2-inch blocks were bolted to the ends of the crosspiece, but the third block needed further attention, as it was to be used for the rudder or steering runner.

[Ill.u.s.tration: Fig. 167. The Tiller.]

[Ill.u.s.tration: Fig. 168. Drilling the Mast Step.]

The rudder post was shaped from a block of hardwood 3 inches square and 10 inches long. Two inches from the lower end saw cuts were made in the side of the block to a depth of 3/4 inch. Then with a chisel the sides were split off, forming a large pin with a square shank 8 inches long.

Next the corners of the shank were cut off, rounding it to a diameter of 1-1/2 inches. The runner block was fastened securely to the head of the rudder post with screws. A 1-1/2-inch hole was now drilled into the backbone at the stern end to receive the rudder post. A tiller was next cut out of a 1-inch board to the shape shown in Fig. 167. A slot was cut in the end of the tiller, and the latter fitted snugly over the top of the post, where it was held in place by screws threaded in through the sides.

[Ill.u.s.tration: Fig. 169. The Mainsail.]

The mast of our boat was a pole 8 feet long, tapering from a diameter 2 inches at the base to 1-1/2 inches at the top. A step for the mast was cut from a 2 by 4 block 8 inches long. A 2-inch hole was drilled into the face of this block. We had no drill large enough to bore this hole, but accomplished the same result by drilling eight 1/2-inch holes inside of a 2-inch circle (Fig. 168), and then used a chisel to cut off the projecting pieces. The mast step was firmly bolted to the backbone at its thickest part, that is, just four feet from the forward end. The mast was braced with stay ropes stretched from the top to the forward end of the backbone and to the ends of the crosspiece. A 9-foot pole, tapering from 1-1/2 inches to 1 inch in diameter, was used for the boom of the mainsail, and for the gaff we used a 6-foot pole of the same diameter.

[Ill.u.s.tration: Fig. 170. Jaws of the Boom.]

[Ill.u.s.tration: Fig. 171. A Cleat.]

The dimensions of the mainsail are given in Fig. 169. For mast hoops we used curtain rings. Five were attached to the sail along the luff, and one was fastened with a piece of leather to the end of the gaff. We used a different scheme for holding the boom to the mast. The forward end of the boom was flattened at the sides and a couple of cheek blocks were bolted on, forming jaws of the shape indicated in Fig. 170. The jaws were whittled out to fit nicely around the mast, and were kept from slipping off by a piece of rope pa.s.sed around the mast and threaded through the ends of the cheek blocks. Half a dozen small pulley blocks were now procured, of the type used on awnings. A rope called the throat halyard was strung from the throat or forward end of the gaff through a pulley block near the top of the mast, and led down to the backbone, where it was "belayed," or wrapped around a cleat. The cleat, which was whittled out of a stick of wood, was made in the form indicated in Fig.

171. A short length of rope was strung through a pulley block and tied with some slack to the upper end and to the center of the gaff. This rope is called a "bridle," and to the pulley block on this "bridle" a rope was attached called the "peak halyard." The peak halyard was pa.s.sed through a pulley block at the top of the mast, and belayed on a cleat at the side of the backbone. For the main sheet (that is, the rope used for guiding the mainsail) two pulley blocks were fastened to the backbone, one just in front of the seat and the other a few feet further forward, and two more were lashed to the boom, midway between these blocks. The sheet was fastened near the aft end of the backbone and then strung through the blocks in the order ill.u.s.trated, the free end of the sheet being brought back to the seat, where a cleat was provided, to which it could be secured when desired.

[Ill.u.s.tration: Fig. 172. The Jib-sail.]