214: THE RAINBOW 



door of our Alpine cottage. A strong cylindrical cop- 

 per boiler, sixteen inches high and twelve inches in 

 diameter, was nearly filled with water and heated by gas- 

 flames until steam of twenty pounds pressure was pro- 

 duced. A valve at the top of the boiler was then opened, 

 when the steam issued violently into the atmosphere, 

 carrying droplets of water mechanically along with 

 it, and condensing above to droplets of a similar kind. 

 A fair imitation of the Alpine atmosphere was thus 

 produced. After a few tentative experiments the 

 luminous circle was brought into view, and having once 

 got hold of it, the next step was to enhance its in- 

 tensity. Oil-lamps, the lime-light, and the naked elec- 

 tric light were tried in succession, the source of rays 

 being placed in one room, the boiler in another, while 

 the observer stood, with his back to the light, between 

 them. It is not, however, necessary to dwell upon these 

 first experiments, surpassed as they were by the arrange 

 ments subsequently adopted. My mode of proceeding 

 was this. The electric light being placed in a camera 

 with a condensing-lens in front, the position of the 

 lens was so fixed as to produce a beam sufficiently broad 

 to clasp the whole of my head, and leave an aureole 

 of light around it. It being desirable to lessen as much 

 as possible the foreign light entering the eye, the beam 

 was received upon a distant black surface, and it wa 

 easy to move the head until its shadow occupied the 

 centre of the illuminated area. 



To secure the best effect it was found necessary t( 

 stand close to the boiler, so as to be immersed in th 

 fog and drizzle. The fog, however, was soon discovere 

 to be a mere nuisance. Instead of enhancing, it blurre 

 the effect, and I therefore sought to abolish it. Allow 

 ing the steam to issue for a few seconds from th 

 boiler, on closing the valve, the cloud rapidly melte 



