GARDENING AS A SCIENCE. 



451 



a ray of solar light. They, and others snico 

 their time, not only succeeded in proving 

 this, but also made it apparent that different 

 heating powers were possessed by the ray 

 when so divided. It will not be out of the 

 way to notice these briefly. 



When a sunbeam is made to pass through 

 a triangular piece of polished glass, called 

 a prism, an oblong image, termed a spec- 

 trum, is produced, which displays on a white 

 screen seven primitive colours, — red, or- 

 ^^S^i yellow, green, blue, indigo, violet. 

 The white sunbeam, as everybody knows, 

 produces a sensation of heat on the hand ; 

 yet it communicates no degree of warmth 

 to a piece of glass through which it passes, 

 as, for instance, a burning glass. But, de- 

 compose the ray, and it at once exhibits 

 very different degrees of heat ; thus, — " on 

 applying a delicate thermometer, it is seen 

 that the blue ray scarcely affects it at all ; 

 in the green it rises, and in the red shows 

 an increase of several degrees. Assuming 

 the heating power of the violet ray at 16°, 

 that of the green is 26°, of the red 55^; but 

 beyond the red ray, and the limits of the 

 visible spectrum, the increase of tempera- 

 ture is still greater." 



These phenomena, though inconclusive, 

 are nevertheless interesting ; and they have 

 been rendered more so by the recent obser- 

 vations of Dr. Horner, of Hull ; for these 

 have made it probable that glass of differ- 

 ent colours may be of use to the gardener 

 in effecting different objects ; thus, blue 

 glass is supposed to favor the first principles 

 of growth, and to assist the germination of 

 seeds, and, by inference, the protrusion of 

 roots from cuttings ; while the red, or heat- 

 ing colour, and the brilliant illuminating 

 yellow, are more favorable to the processes 

 of maturation. 



The unity of creation, the universality of 

 light, seem to require, and indeed, prove. 



that one simple, vivifying principle is, and 

 has been in active operation from the com- 

 mencement of time. Professor Playfair 

 once observed — '• If we consider how many 

 different laws seem to regulate the action 

 of impulse, cohesion, elasticity, chemical 

 affinity, crystallization, heat, light, magnet- 

 ism, electricity, galvanism, the existence of 

 a principle more general than these, and con- 

 necting all of them with that of gravitation^ 

 appears highly •probable^'' 



Such was the almost prophetic sugges- 

 tion of this philosopher. That the globe 

 was " cavei'Tious, replete with light, shining 

 with intense splendor,''^ was the presumption 

 of a Leslie. But if, as we believe the fact 

 to be, solar light is the only ethereal es- 

 sence or matter which pervades all nature, 

 no such cavernous central magazine of it is 

 required ; nor need we perplex our minds 

 about the source of effulgence, for the glo- 

 rious sun stands revealed to all ; and the 

 life and activity of creation depend ixpon 

 his beams. View it in any way we please, 

 the command — " let there be light,'" was the 

 language of power ; the fiat gave life to all 

 created things, and there is not one act of 

 progress or increase, of respiration, decom- 

 position, motion, electrical or chemical ac- 

 tion, that is not, and ever has been, depend- 

 ant on it for its commencement, continua- 

 tion, and completion. Let those who doubt 

 consider the wonderful orb, whose beams 

 have been poured upon the planetary sys- 

 tem throughout time ; let them, with phi- 

 losophic eyes, view the mighty phenome- 

 na of development and increase that are 

 manifestly the result of his power, and they 

 will find themselves constrained either to 

 admit that light is absorbed by the bodies 

 upon which it strikes, or that it becomes 

 extinguished and lost ; the latter conclusion 

 would be subversive of the analogy of all 

 nature. 



