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 atmo- 

 sphere was thus produced. After a few tentative ex- 

 periments, the luminous circle was brought into view, 

 and having once got hold of it, the next step was to 

 enhance its intensity. Oil-lamps, the lime-light, and 

 the naked electric 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 arrangements subsequently adopted. My 

 mode of proceeding was this. The electric light being 

 placed in a camera with a conden sing-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 de- 

 sirable to lessen as much as possible the foreign light 

 entering the eye, the beam was received upon a distant 

 black surface, and it was easy to move the head until 

 its shadow occupied the centre of the illuminated area. 

 To secure the best effect it was found necessary to 

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

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

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

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

 ing the steam to issue for a few seconds from the 

 boiler, on closing the valve, the cloud rapidly melted 



