LIGHT. 105 



the figure. Moving it towards the screen, beautiful 

 colored figures will appear, which will change with the 

 angle of the second lens to the light that is incident 

 upon it. A comet, a hollow funnel, a mock sun, and 



Fig. 8O. 



other curious forms may be projected, all of them 

 brilliantly colored. 



With a lantern, it will be sufficient to remove the 

 objective and place a large lens, like one of the above, 

 near the focus of the condenser, when the same figures 

 will appear. 



DISPERSION 



Is usually shown by decomposing a beam of solar light 

 with a triangular prism. The beam should be a rather 

 small one, not more than one fourth of an inch in 

 diameter, if a pure spectrum be wanted. If it be more 

 than this, there will be more or less white light in the 

 middle of the band. 



Fig. tfl. 



The smaller the aperture, the purer will be the colors 

 into which the light has been decomposed ; but if a 



