64 THE REASON WHY. 



" Consider the lilies of the field, how they grow ; they toil not, neither do they 



spin. 



When we gaze upon a rose it is not its beauty alone that should impress us : 

 every moment of that flower's life is devoted to the fulfilment of its part in the 

 grand scheme of the universe. It decomposes the rays of soiar light, and scuds 

 the red rays only to our eyes. It absorb 4 or radiates heat, according to the 

 temperature of the aerial mantle that wraps alike the flower and the man. It 

 distils the gaseous vapours, and restores to man the vital air on which he lives. 

 It takes into its own substance, and incorporates with its own frame, the car- 

 bon and the hydrogen of which man has no immediate need. It drinks the 

 dew-drop or the rain drop, and gives forth its sweet odour as a thanksgiving. 

 And when it dies, it preaches eloquently to beauty, pointing to the end that is 

 to come I 



CHAPTER XII. 



226. Sow do we know that plants operate upon the solar 

 and atmospheric neat ? 



A delicate thermometer, placed among the leaves and petals of 

 flowers, will at once establish the fact, not only that flowers and 

 plants have a temperature differing from that of the external air, 

 but that the temperature varies in different plants according to the 

 hypothetical or supposed requirements, of their existences and 

 conditions. 



227. What is the chief cause of variation in the tempera- 

 ture of flowers ? 



It is generally supposed that their temperature is affected by 

 their colours. 



228. WTiy is it supposed that the colour of a flower influ- 

 ences its temperature / 



Because it is found by experiment that the colours of bodies bear 

 an important relation to their properties respecting heat, and hold 

 some analogy to the relation of colours to light. 



[If when the ground is covered with snow, pieces of woollen cloth, of equal size 

 Mid thickness, and differing only in colour, are laid upon the surface of the 

 snow, near to each other, it will be found that the relation of colour to 

 temperature will be ns follows : In a few hours the black cloth will have 

 dissolved so much of the snow beneath it, as to sink deep below the surface; 

 the blue will have proved nearly as warm as the black ; the brown will have 

 dissolved less of the snow ; the red less than the brown ; and the ivhite the least. 



