96 



DESCRIPTION OF THE PLATES. 



PLATE Z, coloured, \sfig. loa, and lol), plate V., as seen when in motion . 

 PLATE II., coloured, is fig. ii, plate Y., as seen when in motion. 

 PLATE III., coloured, is fig. 4, plate V., as seen when in motion. 



PLATE IV.— Fig. 1, vide page 58. 



Fig. 2. Form of machine. Small wheel makes eight revolutions for 

 one of large ; a, nut for fixing on the discs ; b, nut for fixing figures 

 when the motion is perpendicular. They are moveable, being merely 

 screwed to the spindle. 



Fig 3. Diagram to explain theory of horizontal motion. 



Figs. 4, 5, 6, 7, 8, 9, and figs, i and 2 in plate V., various forms of 

 discs and half discs described. 



Fig. 8, a disc with several concentric rings, white and black alter- 

 nately. 



'Fig. 9, and figs, i and 2 in plate V., are an analysis of the preceding 

 fig. when made to move by excentric motion. 



Fig. 9 is a semicircle similar to fig. 8. Several concentric circles are 

 drawn. Then with another centre, one half the breadth of one of the 

 rings from the former centre, other circles are drawn so as to divide 

 each ring into two, diagonally. Half of each ring is painted black. If 

 the half of the first is painted black on the right, the half of the next 

 is painted black on the left, and so on alternately. When revolving on 

 first centre it produces an eflect similar to fig. 8 when excentric. Each 

 alternate ring has a difiereut colour. 



PLATE V. — Figs, i and 2 are a further analysis oifigs. 8 and 9, plate VI. 



Fig. I produces one series of colours ; fiig. 2, the other series ; or by 

 reversing the motion, the one disc produces the same effect as the other. 

 Fig. I when moving from left to right, as the hands of a watch, produces 

 a reddish-brown, shading off to yellow. Fig. 2, when moving in the 

 same direction, produces a kind of gloomy green. In the one the light 

 begins bright and becomes fainter ; in the other it begins faint and 

 becomes brighter. 



Fig. 3. A sort of spiral to produce gradation of colour. From the 

 predominance of the white, when the light is increasing, the ring on the 

 rims is a bright yellow ; at times very bright. 



Fig. 4. A spiral, for a similar purpose as fig. 3, only the shade pre- 

 dominates, and the rim is consequently of a beautiful green. These 

 produce splendid effects, both by perpendicular and horizontal motion. 

 {See plate III.) 



Fig. 5. Diagram to explain the theory of perpendicular motion. 



Figs. 6, 7, 8, 9, are merely varieties oifig. 5 ; the explanation of which 

 must be kept in view when studying the effects produced by these 

 figures. 



Figs, loa and 106, when revolving produce the appearance repre- 

 sented on plate I. ; A and 5 are the obverse and reverse of the card. 



Fig. II, when put into motion produces the coloured image shown on 

 plate II. The obverse and reverse of this card are identical, as the 

 black parts are cut out. 



The horizontal discs are reduced in size ; those by which the experi- 

 ments were made were about six inches in diameter. 



