TIIK SUN'S SPECTRUM 157 



II tr.iMMi.it ted considerably more light than the red 



y remedied the former inconvenience of an 



arising from heat Repeating theae trial* 



veral time*, 1 constant! i the same rent. 



w to see the RUM diitim-tly without inconvenience 



danger from the heat continued to occupy his 



thought* for years. I w.-d th- MUI through 



water," he wrote in 1801. "It keeps the heat off so 



il. that we may look for any length of time, with- 



least inconvenience.' ' Ink <liluti with water 



gave an image of the son as white as snow ; and I saw 



locts very distinctly, without darkening glasses." 



M-li.-l intrdiuvd his papers on the sun's light 

 ft ml heat with a wise remark, which proved him to be 

 as good an observer in the world of mind as in that of 

 It is sometimes of great use in natural philo- 

 sophy to doubt of things that are commonly taken 

 mtetl; especially as the means of resolving any 

 doul.t. when once it is entertained, are often within 

 .r reach. ... It will therefore not be amiss to notice 

 iat gave rise to a surmise, that the power of heating 

 and illuminating objects might not be equally di- 

 ted among the variously coloured rays." The ex- 

 it nenta, which he then made on the light and heat 

 <>ut by each colour of the spectrum, were admir- 

 ly imagined and beautifully carried out He was really 

 ^aged on a continuation of Newton's experiments on 

 sunbeams, but the field of research was new and untrod. 

 Gradually the questions to which he sought answers 

 ;an to take shape more distinctly in his mind. 

 i prism intercepts a beam of sunlight, let into 

 a darkened room through a hole in the window shut 

 and the band of coloured light, five times as long as it 



