97 



as far as the usual beginning of red. In other words, what we call 

 ■orange and yellow are not pure colours at all ; the former may 

 be represented as 2 R. + 1 G. and the latter as 1 R. + 2 G. , the 

 three primary colours being really red, green and blue, all others 

 are the results of combinations.! 



There is a curious feature in the spectrum of the sun to be 

 considered. The solar spectrum is found to be full of black lines 

 across it. When first discovered, no explanation could be given ; 

 T>ut when the spectrum of the monochromatic light of sodium (as 

 when salt was put in burning spirit in the old days of " snap- 

 dragons " at Christmas) is examined a pure yellow light without 

 any other colour is seen. On comparing this with the solar spec- 

 trum, where the latter showed a black line only, the spectrum of 

 sodium showed a yellow one only, in exactly the same place. This 

 was the first coincidence. When by vaporising other substances, 

 many other coincidences were discovered, as of iron, so many had 

 been exactly " matched " that it was felt we were justified in 

 saying the lines represented the same substances in luminous 

 vapours round the sun. The black lines mean that in passing 

 through the vaporous coverings of the sun some portions of light 

 get absorbed and do not reach the earth. Some may also be 

 absorbed by our atmosphere. Now let us turn to chlorophyll. 

 By pouring spirits of wine upon some macerated leaves and strain- 

 ing it, a green solution of chlorophyll can be obtained, and, 

 looking at this, held up to the light, through the spectroscope, we 

 find seven black bands ; indicating the fact that the sun-light is 

 partly absorbed by the chlorophyll. We infer, therefore, that the 

 two in the orange and two in the blue are the chief elements of 

 sun-light required in the process of assimilation of carbon out of 

 the CO 2 from the air. 



What is the result? Omitting primary effects of the mysteri- 

 ous process effected by light, the first visible product is starch- 

 grains arising on the surface of the chlorophyll granules. These 

 increase in size till little of the chlorophyll-granule to which they 

 are due can be seen. The starch grains of different plants vary in 

 size and other details, so that they easily betray their origin. Thus 

 potato-starch is very large with concentric rings, rice starch is 

 very small, arrowroot has rays marked out, etc. Hence adultera- 

 tions of arrowroot can easily be detected with the microscope. 

 Having seized the carbon out of C0 2 , the oxygen is dismissed 

 and sent back into the air; thereby purifying it again, for C0 2 is 

 an impurity, ever on the increase from the above mentioned 

 sources. 



Having thus started with the manufacture of starch, nothing 

 can be done with it until it can be dissolved, so that Life directs 

 the forces involved in working out chemical changes in all organic 

 products and converts starch into sugar. Starch being C 6 H 10 0 5 , 



t Prussian blue with gamboge makes green, because the green over- 

 powers, and 1 Blue -f 1 Red + 2 Green = Green (to the eve). 



