Fig. 64. Sundial
"Go to our jeweller in the city and get him to give you an old tin clock-dial, like the one shown in [Fig. 64]. If you cannot get one, make a dial out of cardboard yourself, printing the hours in ink. Slit the dial from the centre to a point directly underneath the number 12, if you have Arabic numerals on your dial.
"Then cut out a triangular blade or gnomon, like the one shown. If your dial is of tin, make the blade of tin, or cardboard if your dial is of cardboard.
"Insert the blade in the slit of the dial and secure it to the top of the stand you have selected—with tacks if your dial is cardboard, with small nails if it is tin. Then your sundial will be completed and ready for business.
"At 12 o'clock, there will be only the shadow of the thin edge of the blade over the dial, but as the sun moves, so will the shadow, so as to tell always the correct time of day. You will find this not only a useful but a quaint and artistic addition to the grounds, and not at all expensive."
"Papa," said George, "mamma wants a flower bed made in the front garden, and she would like to have it an oval or elliptical shape. I have promised to make it for her, but I do not know how to make the shape, and I wish you would tell me."
"Certainly, my boy, I will show you. It can be done easily with a string and two wooden pegs. Follow the lines I make on the blackboard. First we must decide on the length and width of the oval or rather ellipse required. Then draw two straight lines, A B and C D, [Fig. 65], equal to the two axes, and bisect or halve each at right angles. Set off from C half the length of the great axis at E and F, which are the two foci of the ellipse. Take an endless string, as long as the three sides of the triangle, C E F, fix two pins or nails in the two foci, one at E and one at F. Lay the string around E and F, stretch it with a marker G, and it then will describe the desired ellipse.
Fig. 65. Drawing an ellipse