I want to use this post to give you an idea of my thought processes in adding the dome. First of all, when I made the Horizontal Channels, I did not measure correctly the width of apparatus, so instead of covering the whole table, I was left with a little ledge on each side of the table.
There was also a larger area in the back of the apparatus that was left uncovered because in setting up the ramp, the apparatus had to be pulled six inches further down the table leaving a bare space on the end opposite the ramp.
Those measuring mistakes gnawed at my brain. I began to wonder if I could extend the channels. I could have added a separate channel on the back perpendicular to the others. As I thought about it more, though, I realized the ledges could offer strong support for a box placed over the channels. The question was: Do I cover all or some of the channels? I decided I only wanted to cover part of the channels because I wanted to keep a certain amount of the lateral play that this apparatus seems to fostered.
The next question was: Can I find a big enough box to span the channels and cover the back ledge, but not the whole table? My question was answered the next morning---literally. When I came into work, I saw a very nice box that looked like the right size sitting in the front hallway of the school. I asked the custodian why was there a box in the front hallway. He told me he had set it aside for me. The custodian really had no idea I was looking for a box with just the right dimensions for the dome. He is in my room every day, though, so he knows I appreciate a sturdy box. How is that for luck?
Once I had the box, a decision had to be made about where to position it over the channels. There was one overriding factor that determined the placement of the box. I wanted to attach a vertical chute that would empty into a tub off the end of the table. That meant the box had to stick out far enough over the table to accommodate the vertical chute and the tub into which it emptied .
Below is a picture of the vertical chute seen from the inside of the box.
Once the position of the box was established, I had to decide on the placement and size of the holes. The holes on three sides were easy. I wanted the holes to be big enough so the children could reach inside, not just with their hands, but also with their body. I also wanted the holes to act like windows so children could interact through them.
The hole on the top of the box was also an easy decision. I knew I needed one on top because children will work on all levels of any apparatus (Axiom # 3 on the right-hand column of the blog). Without a hole, corn would collect on top and then be brushed off onto the floor. Providing a hole on the top created an outlet for the need to work with corn on the highest level. In the picture below, the child is watching his own action of pouring corn through the hole on top.
But I did not want the top hole to be too big because the top itself offers another valuable space for children's play.
The hardest decision for me was the shape of the holes in front. I could have done one big hole like I did with the other three sides, but for stability I wanted some of the holes resting on the channels. I decided to cut a big hole over the large channel. I decided to cut the holes over the narrow channels the height of the channels themselves. That gave the dome stability and also created obstacles for moving the corn or vehicles through the narrow channels under the dome.