262 ON A DYNAMICAL TOP. 



NOTE. 

 Dimensions and Weights of the parts of th Dynamical Top. 



I. Body of the top- 

 Mean diameter of ring, 4 inches. 

 Section of ring, $ inch square. 



The conical portion rises from the upper and inner edge of the ring, a 

 height of 1| inches from the base. 



The whole body of the top weighs . 1 Ib. 7 oz. 



Each of the nine adjusting screws has its screw 1 inch long, and the 



screw and head together weigh 1 ounce. The whole weigh . 9 



II. Axle, &c. 



Length of axle 5 inches, of which inch at the bottom is occupied by 

 the steel point, 3 inches are brass with a good screw turned on it, 

 and the remaining inch is of steel, with a sharp point at the top. 



The whole weighs 1 



The bob B has a diameter of 1'4 inches, and a thickness of '4. It weighs 2f 



The nuts 6 and c, for clamping the bob and the body of the top on the 



axle, each weigh ^ oz. . 1 



Weight of whole top 2 Ib. 5\ oz. 



The best arrangement, for general observations, is to have the disc of card divided 

 into four quadrants, coloured with vermilion, chrome yellow, emerald green, and ultramarine. 

 These are bright colours, and, if the vermilion is good, they combine into a grayish tint 

 when the revolution is about the axle, and burst into brilliant colours when the axis is 

 disturbed. It is useful to have some concentric circles, drawn with ink, over the colours, 

 and about 12 radii drawn in strong pencil lines. It is easy to distinguish the ink from 

 the pencil lines, as they cross the invariable axis, by their want of lustre. In this way, 

 the path of the invariable axis may be identified with great accuracy, and compared with 

 theory. 



