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 shifted 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 screwing up the trunnion and swivel nuts.  But the sun mirror had to be constantly shifted 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, shift 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 shifted 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.

[Illustration:  Fig. 162.  Top View, showing position of the Two Mirrors and the Screen.]

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 canal, 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.