Our young friends would, we doubt not, like to know how to make a sun-dial that will give the time very accurately. Common sun-dials depend on the shadow of a post, which is thick and heavy, and affords only a very rough idea of the time. But the one we are going to tell them about will show the time as precisely as a clock. And it is quite easy to make. It has, in the first place, a face set up slanting on a pedestal. The proper slant answers to the latitude of the place. At and near New York it should be about forty-one degrees from the perpendicular, or a little more than half upright. The face is divided into hour spaces, just like the face of a clock, but the whole circle is not used. A semicircle is all that the sun can traverse, except in the long days of summer. The fourth part of a circle is about all that can be used in ordinary windows. It will answer for the hours between nine o'clock and three. It is divided into six equal parts for the hour spaces, and each of these is subdivided for the minutes. If the radius of the circle be one foot, the minute spaces will be about one-sixteenth of an inch, or about the same as on the face of a watch. The dividing is easily done with a pair of compasses, a ruler, and a sharp lead-pencil.
Now we will explain the indicator. It is made of three pieces--a base and two uprights. The base is fifteen inches long, three wide, and three-quarters of an inch thick. The uprights are of the same thickness, and about seven inches high. They are morticed into the base, and have the shape shown in the picture. A hole half an inch in diameter is bored through the upright at A, and another at B. Over each of these holes pieces of tin are tacked, with a little hole in the centre about as large as a pin's head. When the sun-dial is placed in position, the sun shines through these holes, and makes a little bright circle on the other upright. The upper hole, A, is for summer, when the sun is high, and the lower one, B, for winter. The indicator is pivoted by a large screw to the centre, C, of the face, so that it can be turned round like the hand of a clock. At the upper end of the indicator a little pointer is fastened directly over the scale of hours and minutes. A needle, or a pin with the head cut off, makes a good pointer.