58 



COLOUR, FORM, AND MOVEMENT. 



At tliis point pupils might be asked to name common 

 coloured natural objects, whose colour is due to these ob- 

 jects absorbing certain rays of light and reflecting others : 

 Examples : Flowers, vegetables, fruits, butterflies, feathers, 

 birds' eggs, etc. 



Amongst the examples given there are likely to be some 

 whose colour is due to the structure of the object on which 

 the light falls. In this case the colour will vary as the 

 object is moved in the light (it varies with the angle of 

 incidence of the light). This will be best understood by 



UUTRA-VIOLET 



VIOLET 



INDIGO 



BLUE 



G/*EEN 



YELLOW 



ORANGE 



RED 



INFRA-RED 



Fig 4. White light passing through a prism is broken up into its 

 constituent elements. 



citing more examples and comparing with those already 

 quoted : Pearls or mother of pearl, many feathers, e.g. the 

 tail feathers of the magpie or breast feathers of the 

 starling, the metallic colours exhibited by many beetles, 

 the cuticle of an earthworm, the iridescent scum upon a 

 stagnant pool. 



It will not be difficult for the pupils to understand that 

 in some cases the colour of an object may be due to both 

 causes combined, viz. a substance absorbing certain light 

 rays and at the same time, owing to the structure of its 

 surface, producing a play of colour by means of the rays 

 which are reflected. Some of the instances quoted, e.g. 

 feathers showing reflections (starling, magpie) , are of this 

 nature, 



