2 NATURE-STUDY REVIEW [17:1— Jan., 1921 



London in 1288 A. D, and one was in use on Dover Castle in 1348; 

 and by 1400 there were clocks made resembling those we have now. 

 It is well for us all to think of the many, many centuries of hirnian 

 histon^ which passed with their days marked only by the shadow 

 of the sun upon a dial. 



In order to make the construction of the sun-dial of greatest use 

 in a school, all the pupils of a suitable age should make working 

 plans for a dial; these may be made on ordinar\^ drawing paper 

 and the gnomen may be made of card-board and cut out and set 

 in place with pins. After the plans are made, even to the inscrip- 

 tion, one of them sliould be chosen, because of its excellence, as 

 the model to be followed in the manual training class in making the 

 dial to be set up in the school yard. 



HOW TO MAKE THE PLANS FOR A SUN-DIAL 



Take a piece of drawing paper about 16 inches square, find its 

 exact center and draw upon it a square with sides 14 inches; find 

 the center of the square, y. Draw on it with a pencil the line 

 AA" a foot long and one-eighth inch at the left of the center. 

 Then draw the line B B" exactly parallel to the line A A" and a 

 fourth inch to the right of it. These lines should be one- fourth 

 inch apart — which is just the thickness of the gnomon. 



With a compass, or a pencil fastened to a string draw the 

 half-circle A A' A''' with a radius of six inches with the point C for 

 its center. Draw a similar half-circle B B' B" opposite with c' for 

 its center. Then draw the half-circle from D, D', D", from c with 

 a radius of five and three-quarters inches. Then draw similarly 

 from c' the half-circle E, E', E". Then draw from c the half-circle 

 F, F', F" with a radius of five inches and a similar half-circle G, 

 G', G" from c' as a center. 



Find the points M, M' just six inches from the points F, G; 

 draw the line J, K through M, M' exactly at right angles to the 

 fine A, A'. This will mark the six o'clock point so the figures VI 

 may be placed on it in the space between the two inner circles. 

 The noon mark XII should be placed as indicated (the "X" at D, 

 F, the "11" at E, G). With black paint outline all the semi- 

 circles and figures. 



