POWER OF SHORT SPACES. 



43 



square, the second into two rhombs which are united at their 

 edges, the third forms the triangular prism, the fourth presents 

 an image of the cube, the fifth of the rhomhohedron, the sixth 

 of the regular hexagonal prism, while the seventh forms a very 

 beautiful image of the cylindrical tube. All these figures 

 appear hollow, and their terminal planes are filled in bj the 

 imagination. 



Hitherto we have assumed the existence of a single linear 

 aperture at the distal extremity of the instrument, and hence 

 the production of a single image ; but we can by increasing 

 the number of the apertures multiply the images, just as when 

 an object is held in the pencils of light proceeding from many 

 simple perforations, and from the same cause. 



The relative position and distance of the apertures will also 

 regulate the disposition of the images ; thus if they are arranged 

 at regular intervals the images will be so also, and if in rays 

 proceeding from a common centre the images will radiate in 

 like manner. Several composite forms of considerable beauty 

 are thus produced. 



If, for example, a small hexagon drawn in transparent out- 

 line (fig. 19), be viewed in the light admitted pj„ 

 through several alternating and equidistant linear 

 apertures, thus (fig. 21), there will be seen the 

 images of as many regular hexagonal prisms 

 having the same relative position ; and the result- 

 ing compound form will present a beautiful 

 honeycomb appearance, as in the following figure (fig, 22). 



If a transparent circle in outline (fig. 20) is substituted for 

 the hexagon, the resulting form presents an analogous arrange- 

 ment of cylindrical tubes, as in fig. 23, 



21. 



o 



Fig. 22. 



Fig. 23. 



Were I not afraid of tiring the patience of my readers, I 

 might here proceed to describe and delineate a considerable 

 variety of beautiful figures, which are produced when the 

 apertures at the most distant extremity of the instrument are 

 tinted with different colours. The introduction of tints in 



