r 20 Transactions of the Society. 



ii. Description of a Model Producing an Optical Effect similar to 

 the Cuneate Markings on Insect Scales. 



In order to test the theory of the production of these markings 

 by the crossing of tubes at various angles, many experiments were 

 made with glass rods, ribbed glass, and tubes filled with various fluids. 

 As a result of these experiments a model was prepared [exhibited], 

 consisting of two sets of parallel thin glass tubes in contact with 

 each other. The tubes were filled with liquids and sealed at both 

 ends. One set of tubes was fixed stationary in a cell and the other 

 set placed in contact with them, but free to revolve over a consider- 

 able angle. The best results were obtained by using oil of turpen- 

 tine in one set of tubes and ethyl-alcohol in the other. It was 

 found that, by illuminating this model obliquely and varying the 

 angles at which the tubes crossed, all the appearances of beaded, 

 " exclamation " and cuneate markings could be produced. By modi- 

 fying the source of illumination and interposing various objects 

 between the light and the model, numerous images resembling the 

 secondary structure could be produced. The crossing of the tubes 

 creates a series of lenses, like a compound eye, each one capable of 

 forming a separate image. 



