OBSERVATION OF LIGHT. 129 



hour ; and there is a gradual change throughout 

 the seasons. In the spring, the red and the oxy- 

 dizing heat, as well as the fading of the blue into 

 the violet tints, and the de-oxydizing energy of 

 that end of the spectrum, are busily at work in 

 bringing forward all the young leaves of the year ; 

 so that the yellow and the blue are sent back to 

 refresh the eye with the lovely green the indi- 

 cator of the greatest action in the majority of 

 vegetables. Thus, when the plants of the season 

 and the annual shoots of the trees have attained 

 their full size, and the seeds of the future succes- 

 sions are about to be prepared, the oxydizing 

 action becomes less in the delicate texture of the 

 flowers ; and most of their petals absorb chiefly 

 either the yellow or the blue, so that they seldom 

 give back the green. The colours approximate to 

 the golden yellow, the orange, and the intense 

 red, in proportion to the warmth of the climate 

 and the year, and also to the advanced heat of the 

 season. Few early plants have red flowers, though 

 some of them are tinted with pink. In cold 

 places, also, there are not many of the flowers 

 red, while the little ones on the stony and warm 

 moors, even at considerable elevations, are of that 

 colour. Tropical vegetation, on the other hand, 

 is rich in scarlet and gold, and the tints of the 

 flowers of early autumn are the richest in the 

 whole season. Autumn is rich in hues for a 

 while ; but they are, like the hectic flush on the 

 cheeks of the consumptive, the signs of dissolu- 

 tion, and when they have passed, the dingy hue 

 of winter is put on. In the northern regions, 

 the snow serves as a mantle to cover the earth, and 

 suspends all action between its surface and the sun, 



