“It is all ready now. See how easy it is to put together, Donald,” said Polly, as she bent up the front of a bucket and slipped one of its extensions through a slot in one of the disks and the other extension through a slot in the other disk, and then secured them in place by sliding a bolt through the slot in each extension. (Fig. 7.)

“Better glue those bolts down,” said Donald. “When the wheel turns fast they may drop out.”

By this time Donald had gathered together all the materials for his sand tower. For the base of the tower he used an empty cigar box, eight inches long and two and one-quarter inches deep, and for the reservoir a cocoa can four inches high and two inches wide at the narrow sides. On each of the wide sides of the can, about one and one-half inches from the top and at equal distances from the side edges, he made a hole by driving a large wire nail through the tin. (I, Figure 4.) In the bottom he cut with a can opener a large hole, as shown in Figure 4. This hole is not in the middle, but at the back, left-hand corner as the can stands upside down. (Figure 4.)

“The funnel goes through this hole,” Donald said. “I have made a funnel for the sand because it holds more than the can and because only a part of the sand will run out of the can without it.”

Donald made the funnel of a piece of strong paper twelve inches square. He twisted this into a cornucopia and then trimmed it off evenly at the top and cut the point off at the bottom. He enlarged the bottom opening several times in order to allow a sufficient flow of sand to turn the wheel easily. The lapped edges he pasted securely together. To hold the reservoir up he whittled out of an old shingle two uprights like Figure 5. Each upright was thirteen and one-half inches long and three-quarters of an inch wide, except at the top, where it widened out to one inch. Three-quarters of an inch from the top edge he bored a hole large enough to admit a very large, spikelike wire nail a little over four inches long and quite thick.

“I am going to spike these on,” Donald said, thrusting the large nail through the hole in one upright, then through both holes in the can and through the hole in the other upright. “It is a little loose, though,” he continued, shaking the can.

“Put a cork on the end of the spike,” said Polly; “that will hold it.” Donald took her advice and pushed a large, flat cork up on the nail until it fitted snugly against the tin and held it firmly in place. Then he took up the cigar box. “Will you make a hole in this for the shaft of the wheel, Polly? Put it just here,” he said, indicating a spot two and one-half inches from the top and half an inch from the left-hand edge as the box stands on end. (J, Figure 6.) “Bore it with a hot wire nail; it will make a smoother surface than the gimlet.”

Then Polly, holding her hot nail with a pair of pincers, burned a small round hole in the cigar box and also the hole K in the front upright, Figure 8. This front upright, which was to hold the outer end of the wheel shaft, Donald had whittled from a shingle. He made it six and one-quarter inches high, with a base three and one-half inches wide. Polly was careful to have the hole in the upright the same distance from the bottom of the box, so that the shaft of the wheel would be perfectly horizontal when put through the two holes. Donald used small wire nails for fastening the side uprights to the cigar box. He removed the lid of the box, so that he could easily get at the inside, then drove the nails through the uprights into the side, top and bottom edges of the box. (Figure 6.)

“I think we will have to nail the tower and other things to a board,” he said. “They will never stand firm on the sand.” A suitable piece of board could not be found, but Polly begged an old pastry board from the cook and that made a fine flooring for their machinery. Donald stood the sand tower on the board at the left-hand front corner, with the cigar box base just six and one-half inches from the front edge and four inches from the side edge of the board. “I can tack this down from the inside of the box,” he said, and using two good sized carpet tacks he drove them through the end of the box into the board. “Now get a shaft for your wheel, Polly, and we will put the wheel up before I nail the front upright in place.”

Polly had secured for the shaft of her wheel a long, slender paint brush handle. The brush was a No. 2 bristle oil paint brush, and had cost five cents when new. Exactly at the center of each disk of the wheel she made a puncture and then gradually and with great care pushed her shaft through until the wheel was in the middle and on the largest part of the shaft. Then she cut a medium-sized cork into three slices. The two largest slices she pushed up on the shaft, one from either end, and before settling them in place she put a little glue on the shaft close to the wheel as well as on the inner side of the corks, then pushed the corks up over the glue on the shaft and close against the wheel. In this way the shaft, the corks and the wheel were glued together. “They must all turn together,” Polly remarked, “and not like a wheel on an axle.” On the end of the shaft which was to rest in the hole in the box, she slid the remaining slice of cork, leaving it within three-quarters of an inch of the cork fastened to the wheel. This was to keep the shaft from running too far into the box.

“Be sure you get the right end of the shaft into the box,” Donald cautioned. “Remember, the edges of the buckets bend down when the left side of the wheel is toward you.” (Figure 7.)

“I know,” said Polly. “Now I am going to put this large glass bead on to keep the cork from touching the box. The bead is so smooth and round it will turn easily against the wood.” So Polly put her bead on the shaft and slipped the end of the shaft through the box. “I will put a bead on the inside, too,” she added, “and then a cork to keep it from slipping off, and it will have to be a very small cork or it will rub against the side of the box and the shaft won’t turn.” (Figure 7.)

Meanwhile Donald had been devising a way to hold the front upright erect. “I have it now,” he exclaimed, and cutting a piece of wood half an inch wide and half an inch thick into two pieces four and one-half inches long, he nailed them to the front and back of the lower edge of the upright; then sliding the free end of the shaft through the hole in the upright, he settled the upright in place in front of the box, a little to the left, so that the hole in the box and the hole in the upright were directly opposite each other and the shaft went through true and straight. Then he nailed the supports to the board. (Figure 7.)

When the children adjusted the funnel and filled it with sand they found that to make it work perfectly it was necessary to tilt the can forward in order to send the stream of sand near the outer edge of the wheel, and that something must be invented to hold the can in that position, so Donald quickly whittled out the little brace. (Figure 9.) The brace is five inches long at the bottom, two and one-quarter inches long at the top and one and five-eighths inches high. The V-shaped notch is one inch from the front end.

Fitting the back edge of the can into the notch of the brace, Donald adjusted the brace on top of the box so that the can was held at the required angle and the falling sand struck the wheel in the right place; then with two small nails he fastened it on securely. (Figure 6.) Donald also slipped a thin strip of wood between the back of the funnel and the large nail. The wood rested on the bottom of the can and extended up to the top of the funnel.

“That will strengthen it,” he said. “The wheel works all right; now we will make it move things.”

“Let us have a merry-go-round,” Polly suggested.

“Yes, and a mine. The wheel will draw the miners up in a bucket, and then I think when the merry-go-round turns it will pull a wagon uphill, too,” Donald answered.

“And everything will move at once,” Polly cried delightedly.

“We will have to have a belt spool and a winding spool on the end of this shaft,” Donald said. “The belt spool will connect it with the merry-go-round and the winding spool will draw up the miner’s bucket. The spools must be fastened to the shaft, too, so that they will turn with it.”

As the shaft was too slender to fit the holes in the spools, Polly wrapped it with a strip of newspaper. (L, Figure 7.) She used newspaper because it was soft and would cling. She cut a strip about twelve inches long and two inches wide. This she covered on one side with glue; then sticking one end to the shaft about half an inch from the upright, she wrapped the paper tightly around the shaft, making a number of layers, which, glued together, became a solid mass. Donald had selected two spools and glued the ends together—a medium-sized spool for the belt spool and a small spool for the winding spool. When the glue had hardened on the spools and on the paper roll he covered the outside of the roll and the inside of the spools with glue and pushed the spools up on the shaft until they covered the paper roll and stuck fast. (Figure 7.)